WO2023080130A1 - Anisotropic light-diffusing film, anisotropic light-diffusing film with adhesive layer, and image display device - Google Patents

Abstract

An anisotropic light-diffusing film according to an aspect of the present invention has at least one first layer capable of scattering incident light in the traveling direction of the light, and the ratio (60° brightness ratio / front brightness ratio) between a 60° brightness ratio and a front brightness ratio which are obtained by the following methods is 0.30-0.60 inclusive.　<60° brightness ratio> In the light-diffusing film, the ratio (C/B) between a brightness C in a direction inclined at 60° in a light diffusion direction from the direction of a normal N to a film surface and a front brightness B in the direction of the normal N to the film surface is defined as the 60° brightness ratio.　<Front brightness ratio> The ratio (B/A) between the front brightness B of the light-diffusing film and a front brightness A in the direction of a normal N to a film surface in a blank sample satisfying conditions (1) and (2) is defined as the front brightness ratio.　[Blank sample] Condition (1): The total light transmittance measured in conformity with JIS K7361-1 is 90% or more.　Condition (2): The haze measured in conformity with JIS K7136 is 1% or less.

Description

Anisotropic light diffusion film, anisotropic light diffusion film with adhesive layer, and image display device

The present invention relates to an anisotropic light diffusion film.
This application is based on Japanese Patent Application No. 2021-179414 filed in Japan on November 2, 2021, Japanese Patent Application No. 2021-212116 filed in Japan on December 27, 2021, and Japan on December 27, 2021. Claiming priority based on Japanese Patent Application No. 2021-212117 filed, March 18, 2022, Japanese Patent Application No. 2022-043572, Japanese Patent Application No. 2022-043573, and Japanese Patent Application No. 2022-043574. , the contents of which are hereby incorporated by reference.

A light diffusion film is used as an optical film used in a liquid crystal display.
A light diffusion film is used as a diffuser plate in a liquid crystal display device to obtain a uniform planar light source by planarly scattering the light from the light source. It is used as a screen for

Conventionally, as a light diffusion film, one or both surfaces of the film are roughened, or the surface of the film is provided with a scattering particle-containing layer obtained by coating transparent organic fine particles such as acrylic resin. It is used.
For example, in Patent Document 1, as an excellent light diffusion film that can sufficiently satisfy the elimination of luminance unevenness and the suppression of the angle dependence of luminance, an internal structure containing a diffusion element of organic particles inside a matrix resin A light diffusion film is disclosed in which a light diffusion layer is formed on at least one surface of the diffusion film, and the light diffusion layer is composed of at least a binder resin and particles.

Further, in recent years, an anisotropic light diffusion film that scatters light in a specific direction instead of scattering light evenly has been desired.
Applications of such an anisotropic light diffusion film include the display surface of large-sized liquid crystal televisions, diffusion plates, screens of projection type image display devices such as rear projection televisions, and the like.

For example, in Patent Document 2, as an anisotropic scattering film suitable as a screen of a projection type image display device and excellent in all performances of resolution, contrast, and brightness, at least two or more incompatible resins wherein the phase-separated structure of the immiscible resin is a sea-island structure comprising a sea phase comprising at least one resin and an island phase comprising at least one resin, wherein the island phase comprises The film has a rod-like shape oriented in one direction at least on the surface layer, and is characterized in that the scattered light intensity is different between the scattering plane parallel to the orientation direction of the island phase and the scattering plane perpendicular to the orientation direction of the island phase. An anisotropic scattering film is disclosed.

In addition, Patent Document 3 describes an anisotropic optical film that suppresses glare and abrupt changes in luminance and has an optimized balance of optical properties including light diffusion properties. An anisotropic optical film, the anisotropic optical film having at least one anisotropic light-diffusing layer, the anisotropic light-diffusing layer having a plurality of louver rod structures and a matrix region. and an anisotropic optical system characterized in that the cross-sectional shape of the louver rod structure perpendicular to the direction of the columnar axis is a substantially rounded rectangle formed by connecting both ends of two substantially parallel lines with a substantially circular arc. A film is disclosed.

WO2008/129946 Japanese Patent Application Laid-Open No. 2007-010798 JP 2017-181829 A

For example, as backlight units for large-sized LCD TVs, the mainstream is the direct type, in which the light source is arranged on the back of the liquid crystal panel, or the edge-light type, in which the light source is arranged near the side of the liquid crystal panel.

Backlight units used in large-sized liquid crystal displays are mainly direct type cold cathode ray tube backlight units that use cold cathode ray tubes as the light source from the viewpoint of excellent brightness of the screen and uniformity of brightness within the screen. Used. When a cold cathode ray tube, which is a linear light source, is used as a light source, a plurality of cold cathode ray tubes may be arranged in parallel in order to brighten the display screen. In this case, light from adjacent cold cathode ray tubes interferes with each other, and stripe-like spots of brightness tend to occur.

In recent years, edge-light type backlight units have also come to be used in large liquid crystal displays. As such an edge light type backlight unit, an edge light type LED backlight unit using light emitting diodes (LEDs) as a light source is often used. Parts such as a light plate are required.

Furthermore, in recent years, direct backlight units using LEDs as light sources (direct LED backlight units) have come to be used for reasons such as reducing power consumption and reducing costs by omitting the light guide plate. Such a direct type LED backlight unit generally has an aspect in which the LED light sources are arranged substantially on the same plane as the reflector. In the direct type LED backlight unit, it is desirable to increase the distance between LEDs and reduce the number of used LEDs as much as possible in order to reduce power consumption and manufacturing costs. However, if the distance between the LEDs becomes too large, there is a problem that luminance spots, such as darkening of the corresponding portions between the LEDs, tend to occur in the display device.

Therefore, in order to suppress unevenness in brightness and unevenness in brightness due to the interference of light, a method of using a conventionally known light diffusion film that diffuses light evenly as a display surface or a diffusion plate has been adopted. This method has the problem that the light is diffused in a direction other than the direction in which the viewer views the screen, so that the brightness reflected in the viewer's eyes is insufficient.

In order to obtain brightness of the screen, methods such as increasing the output of cold cathode ray tubes and LEDs and using optical films for improving brightness such as prism sheets are conceivable.
However, new problems, such as image defects such as moire fringes, increased power consumption, and increased member costs, tend to occur.

On the other hand, an anisotropic diffusion film capable of diffusing light in a specific direction can prevent light from scattering in directions other than the direction in which the viewer views the screen. You can expect to be able to solve these problems.

In addition, mobile devices that are expected to be used outdoors have a problem of poor visibility due to reflection of external light. Therefore, a diffuser film with low reflectivity that hardly reflects outside light is useful.

Therefore, an object of one aspect of the present invention is to provide a light diffusion film that is excellent in brightness and visibility when mounted on a display. Another object of the present invention is to provide an anisotropic light diffusion film having both an anisotropic light diffusion property for diffusing light in a specific direction and low reflectivity.

The inventor of the present invention believes that an anisotropic light diffusion film that can diffuse light in a specific direction can prevent light from scattering in directions other than the direction in which the viewer views the screen, enabling viewing at a wide viewing angle. I thought it would be possible to improve the brightness reflected in the human eye. On the other hand, we discovered that if the anisotropic light diffusion is too high, the visibility of the screen when viewed from the front deteriorates. It was found that the brightness and visibility were improved when mounted. Further, as a result of intensive studies by the present inventors, in an anisotropic light diffusion film having a sea-island structure, the anisotropic light diffusion property and the It has been found that both low reflectivity can be achieved.

That is, the gist of the present invention is as follows.
[1] A light diffusion film having at least a first layer capable of scattering incident light in the direction of travel of the light,
An anisotropic light-diffusing film having a ratio of 60° brightness ratio to front brightness ratio (60° brightness ratio/front brightness ratio) determined by the following method of 0.30 or more and 0.60 or less.

<60° luminance ratio>
In the light diffusion film, the ratio (C/B) of the luminance C in the direction inclined 60° from the normal N direction of the film surface to the light diffusion direction and the front luminance B in the normal N direction of the film surface is 60° Let it be the luminance ratio.
<Front luminance ratio>
The ratio (B/A) of the front luminance B of the light diffusion film and the front luminance A in the normal N direction of the film surface in the blank sample satisfying the following conditions (1) and (2) is defined as the front luminance ratio. do.
[Blank sample]
(1) The total light transmittance measured according to JIS K7361-1 is 90% or more.
(2) The haze measured according to JIS K7136 is 1% or less.

[2] The anisotropic light-diffusing film according to [1] above, wherein the 60° luminance ratio is 27% or more.
[3] The anisotropic light-diffusing film according to [1] or [2] above, wherein the front luminance ratio is 80% or more.
[4] The anisotropic light-diffusing film according to any one of [1] to [3] above, which has a surface hardness of B or higher.
[5] The anisotropic light-diffusing film according to any one of [1] to [4] above, which has an arithmetic mean height Ra of 10 μm or less.

[6] The anisotropic light-diffusing film according to any one of [1] to [5] above, which has a haze of 40% or more as measured according to JIS K7136.
[7] The anisotropic light-diffusing film of any one of [1] to [6] above, which has a total light transmittance of 94% or more.
[8] The ratio of the luminous reflectance R _SCE of the specular component exclude method to the luminous reflectance R _SCI of the specular component include method (R _SCE /R _SCI ) is 50% or more, the anisotropic light-diffusing film according to any one of the above [1] to [7].

[9] The anisotropic light-diffusing film according to any one of [1] to [8] above, wherein the first layer has a sea-island structure with the continuous phase (I) and the dispersed phase (II).
[10] The anisotropic light-diffusing film according to [9] above, wherein the volume of the dispersed phase at the central portion in the thickness direction of the first layer is 20 µm ³ or more and 120 µm ³ or less.
[11] The above, wherein the ratio of the average dispersion diameter in the MD direction to the average dispersion diameter in the TD direction of the dispersed phase (II) (MD average dispersion diameter/TD average dispersion diameter) is 3 or more at the center in the thickness direction. The anisotropic light-diffusing film of [9] or [10].
[12] The anisotropic light diffusion according to any one of the above [9] to [11], wherein the dispersed phase (II) has a dispersion diameter area of 2 μm ³ or more in the TD cross section at the central portion in the thickness direction. the film.

[13] The anisotropic light-diffusing film according to any one of [9] to [12] above, wherein both the tensile strength σMD in the _MD direction and the tensile strength _σTD in the TD direction are 50 MPa or more.
[14] Any one of the above [1] to [13], wherein the first layer contains a polycarbonate resin containing a structural unit (a) derived from a dihydroxy compound represented by the following general formula (1): The anisotropic light diffusion film described in .

[15] The anisotropic light-diffusing film of [14] above, wherein the polycarbonate resin further contains a structural unit (b) derived from a dihydroxy compound other than the structural unit (a).
[16] The anisotropic light-diffusing film of [15] above, wherein the structural unit (b) is a structural unit derived from an aliphatic dihydroxy compound and/or a structural unit derived from an alicyclic dihydroxy compound.
[17] The above-mentioned [16], wherein the alicyclic dihydroxy compound is one or more selected from cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol, and pentacyclopentadecanedimethanol. Anisotropic light diffusion film.

[18] The anisotropic light diffusion film according to any one of [1] to [17] above, wherein the first layer contains an amorphous polyester resin.
[19] The anisotropic light-diffusing film of the above [18], wherein the amorphous polyester resin contains a diol component having an alicyclic structure.
[20] The diol component having an alicyclic structure is one or more selected from spiroglycol, isosorbide, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. , the anisotropic light diffusion film according to [19] above.

[21] The anisotropic light-diffusing film of any one of [1] to [20] above, wherein the first layer contains two or more kinds of amorphous polyester resins.
[22] The first layer comprises an amorphous polyester resin and a polycarbonate resin (excluding a polycarbonate resin containing a structural unit (a) derived from a dihydroxy compound represented by the following general formula (1)). The anisotropic light diffusion film according to any one of [1] to [21] above, comprising:

[23] The anisotropic light-diffusing film according to any one of [1] to [22] above, which has a second layer on at least one surface of the first layer.
[24] The anisotropic light-diffusing film of [23] above, wherein the second layer has substantially no dispersed phase.

[25] It has a first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), has a haze of 40% or more as measured in accordance with JIS K7136, and is tensile in the MD and TD directions. An anisotropic light-diffusing film having an intensity ratio (σ _MD /σ _TD ) of 0.75 to 1.25.
[26] It has a first layer having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II), has a haze of 40% or more as measured according to JIS K7136, and has a tensile strength σ _MD in the MD direction. and an anisotropic light-diffusing film having a TD tensile strength σ _TD of 50 MPa or more.
[27] A first layer having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II) is provided, and the volume of the dispersed phase at the central portion in the thickness direction of the first layer is 20 μm ³ or more and 120 μm ³ or less. , the ratio of the average dispersion diameter in the MD direction to the average dispersion diameter in the TD direction of the dispersed phase (II) (MD average dispersion diameter / TD average dispersion diameter) is 3 or more at the center in the thickness direction. .
[28] A first layer having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II), wherein the volume of the dispersed phase at the central portion in the thickness direction of the first layer is 20 μm ³ or more and 120 μm ³ or less. , an anisotropic light diffusion film, wherein the area of the dispersion diameter in the TD cross section at the central portion in the thickness direction of the dispersed phase (II) is 2 μm ² or more.
[29] It has a sea-island structure with a continuous phase (I) and a dispersed phase (II), and at least one of the continuous phase (I) and the dispersed phase (II) contains a thermoplastic resin having an average refractive index of 1.53 or less. An anisotropic light diffusing film, including.

[30] Having a laminated structure comprising at least a first layer and a second layer, the first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), and the second The layer is laminated on at least one surface side of the first layer, and a continuous phase (Ib) containing a thermoplastic resin of the same type as the thermoplastic resin forming the continuous phase (I) of the first layer An anisotropic light diffusion film having
[31] Having a laminated structure comprising at least a first layer and a second layer, the first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), and the second The layer is laminated on at least one surface side of the first layer, has a continuous phase (Ib) containing a resin having a glass transition temperature of 90 ° C. or higher, and has a surface hardness of HB or higher. Anisotropic light diffusion film.

[32] An anisotropic light-diffusing film with an adhesive layer, comprising an adhesive layer on at least one surface of the anisotropic light-diffusing film of any one of [1] to [31] above.
[33] The anisotropic light-diffusing film with an adhesive layer according to the above [32], wherein the adhesive layer contains an acrylic adhesive.

[34] An image display device comprising the anisotropic light diffusion film according to any one of [1] to [31] above.
[35] The image display device according to [34], having a screen size of 32 inches or more.

The anisotropic light-diffusing film according to one aspect of the present invention is excellent in anisotropic light-diffusing properties, transmittance, and low reflectivity, and is therefore excellent in brightness and visibility when mounted on a display. An anisotropic light-diffusing film according to another aspect of the present invention can have both anisotropic light-diffusing properties and low reflectivity.

It is a figure which shows the measuring method of 60 degree luminance ratio. FIG. 4 is a cross-sectional view (MD cross section) of an anisotropic light diffusion film of Test Example 4-1. FIG. 4 is a cross-sectional view (TD cross section) of an anisotropic light diffusion film of Test Example 4-1. FIG. 10 is a cross-sectional view (MD cross section) of an anisotropic light-diffusing film of Test Example 4-2. FIG. 10 is a cross-sectional view (TD cross section) of an anisotropic light-diffusing film of Test Example 4-2. FIG. 10 is a cross-sectional view (MD cross section) of an anisotropic light-diffusing film of Test Example 4-3. FIG. 10 is a cross-sectional view (TD cross section) of an anisotropic light-diffusing film of Test Example 4-3. FIG. 10 is a cross-sectional view (MD cross section) of an anisotropic light-diffusing film of Test Example 4-4. FIG. 10 is a cross-sectional view (TD cross section) of an anisotropic light-diffusing film of Test Example 4-4. FIG. 10 is a cross-sectional view (MD cross section) of an anisotropic light-diffusing film of Test Example 4-7. FIG. 10 is a cross-sectional view (TD cross section) of an anisotropic light-diffusing film of Test Example 4-7. FIG. 10 is a cross-sectional view (MD cross section) of an anisotropic light-diffusing film of Test Example 4-8. FIG. 10 is a cross-sectional view (TD cross section) of an anisotropic light-diffusing film of Test Example 4-8.

An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

<<Anisotropic light diffusion film>>
An anisotropic light diffusion film (hereinafter also referred to as "this light diffusion film") according to one embodiment of the present invention includes a first layer (hereinafter simply referred to as "first (also referred to as "layer").
In the present invention, "capable of scattering incident light in the traveling direction of light" means that the front luminance ratio is 70% or more and the 60-degree luminance ratio is 20% or more.

<Physical properties of the present light diffusion film>
(1) 60° luminance ratio/front luminance ratio In the present light diffusion film, the ratio of the 60° luminance ratio (60° luminance ratio/front luminance ratio) to the front luminance ratio obtained by the following method is 0.30 or more and 0.30. It is preferably 60 or less.
The 60° luminance ratio/front luminance ratio is more preferably 0.32 or more, still more preferably 0.34 or more, and even more preferably 0.36 or more. It is more preferably 0.55 or less, more preferably 0.50 or less, more preferably 0.48 or less, still more preferably 0.46 or less, and even more preferably 0.44 or less.
The fact that the 60° luminance ratio/front luminance ratio is within the above range means that the display has good brightness and visibility both when viewed from the front and when viewed at a wide viewing angle. Therefore, when the 60° luminance ratio/front luminance ratio is within the above range, it can be said that the anisotropic light diffusibility and the front luminance are well balanced.

The 60° luminance ratio and the front luminance ratio are obtained by the following methods.

(60° brightness ratio)
In this light diffusion film, the ratio (C/B) of the luminance C in the direction inclined 60° from the normal N direction of the film surface to the front luminance B in the normal N direction of the film surface (100%) is the 60° luminance ratio (%).
An example of the measuring method is shown in FIG. The light diffusion film 1 is fixed to the backlight unit 2, and light is made to enter from the normal N direction of the film surface (thick arrow in FIG. 1). The luminance C is the measured value when the backlight unit 2 is tilted so that the luminance meter 3 is positioned in a direction tilted 60° from the normal N direction of the film surface to the light diffusion direction y. Further, the luminance B is the measured value when the backlight unit 2 is arranged so that the luminance meter 3 is positioned in the normal N direction.

(front luminance ratio)
The ratio (B/A) of the front luminance B of this light diffusion film to the front luminance A in the normal N direction of the film surface (100%) in a blank sample that satisfies the following conditions (1) and (2). Brightness ratio (%).
[Blank sample]
(1) The total light transmittance measured according to JIS K7361-1 is 90% or more.
(2) The haze measured according to JIS K7136 is 1% or less.
The front luminance A is obtained when the blank sample is fixed to the backlight unit, light is incident from the normal N direction of the film surface, and the backlight unit is arranged so that the luminance meter is positioned in the normal N direction. is the measured value.

(2) 60° Brightness Ratio The 60° brightness ratio of the present light diffusion film is preferably 27% or more, more preferably 30% or more, and even more preferably 32% or more. On the other hand, although the upper limit of the 60° luminance ratio is not particularly limited, it is preferably 99% or less, more preferably 95% or less.
When the 60° luminance ratio is within the above range, the anisotropic light diffusing property of the film is good, and it is possible to prevent light from scattering in a direction other than the direction in which the viewer views the screen. can improve the brightness seen by viewers.

(3) Front luminance ratio The front luminance ratio of the present light diffusion film is preferably 50% or more, more preferably 60% or more, further preferably 70% or more, and 80% or more. is even more preferred. On the other hand, the upper limit of the front luminance ratio is not particularly limited, but is preferably 99% or less, more preferably 95% or less, and even more preferably 90% or less.
When the front luminance ratio is within the above range, the decrease in luminance when viewed from the front can be suppressed, and the visibility of the screen when viewed from the front can be improved. In addition, power consumption can be suppressed when incorporated into an apparatus.

(4) Haze The haze of the present light diffusion film is preferably 10% or more, more preferably 20% or more, still more preferably 25% or more, and even more preferably 30% or more. Furthermore, among them, 40% or more is preferable, 45% or more is more preferable, 50% or more is still more preferable, 60% or more is still more preferable, and 70% or more is particularly preferable. On the other hand, the upper limit of the haze is not particularly limited, but is preferably 99% or less, more preferably 95% or less, and even more preferably 90% or less.
When the present light diffusion film has a structure containing a liquid crystal component, organic fine particles, an anisotropic inorganic filler, or a dispersed phase in a sea-island structure (hereinafter also referred to as a "dispersed component"), a large amount of the dispersed component is present in the film. haze tends to increase. Therefore, when the haze is within the above range, the anisotropic light diffusibility of the film tends to be high.
The haze in the present invention can be measured according to JIS K7136 by the method described in Examples.

(5) Total light transmittance The light diffusion film preferably has a total light transmittance of 85% or more, more preferably 86% or more, even more preferably 87% or more, and 90% or more. is even more preferable, and 92% or more is particularly preferable. Furthermore, among them, it is preferably 94% or more, more preferably 94.5% or more, still more preferably 95% or more, and even more preferably 96% or more. On the other hand, although the upper limit of the total light transmittance is not particularly limited, it is preferably 99% or less.
In the case where the present light diffusion film contains a dispersive component, the total light transmittance tends to be high if there is little reflection due to interfacial peeling between the matrix component and the dispersive component in the film. Therefore, when the total light transmittance is within the above range, the film has low reflectivity and good visibility when mounted on a display.
The total light transmittance in the present invention can be measured according to JIS K7361-1 by the method described in Examples.

(6) Reflectance The present light diffusion film has a reflectance of Specular Component Include method measured using a spectrophotometer, that is, a luminous reflectance R _SCI of 32 or less. It is preferably 29 or less, even more preferably 26 or less, and even more preferably 22 or less. Furthermore, among them, it is preferably 20 or less, more preferably 18 or less, still more preferably 16 or less, and even more preferably 14 or less. On the other hand, the lower limit of the luminous reflectance R _SCI is not particularly limited, but from the viewpoint of anisotropic light diffusion, it is preferably 5 or more, more preferably 5.5 or more.
When the luminous reflectance R _SCI is within the above range, the film tends to have low reflectivity.

This light diffusion film has a specular component exclude method (Specular Component Exclude method) reflectance measured using a spectrophotometer (100%) with respect to the luminous reflectance R _SCI , that is, the luminous reflectance R _{The SCE} ratio (R _SCE /R _SCI ) is preferably 40% or more, more preferably 45% or more, still more preferably 50% or more, and even more preferably 55% or more. , above 60%. On the other hand, the upper limit of the ratio (R _SCE /R _SCI ) is not particularly limited as long as it is 100% or less.
When the ratio (R _SCE /R _SCI ) is within the above range, the film has good light diffusing properties.
The luminous reflectance R _SCI and the luminous reflectance R _SCE in the present invention can be measured by the method described in Examples using a black _background having a luminous reflectance R SCI of 5.1.

(7) Thermal dimensional change rate The light diffusion film has a heat dimensional change rate in the MD direction measured under test conditions of 110°C for 60 minutes in accordance with JIS K7133: 1999, which is 0.5% or less. is preferred, 0.4% or less is more preferred, and 0.3% or less is even more preferred.
When the thermal dimensional change rate is within the above range, it can be considered that the present light diffusion film has sufficient heat resistance at 110° C. or less. Such a film can be suitably used as a constituent member of an image display device mounted on a vehicle.

(8) Surface hardness The surface hardness of the light diffusion film is measured on the surface of the film layer in accordance with JIS K5600 under the conditions of a temperature of 23°C ± 2°C, a relative humidity of 50% ± 10°C, and a load of 750 gf. is preferably B or higher, more preferably HB or higher, and even more preferably F or higher.
When the surface hardness is within the above range, the present light diffusion film can be prevented from being scratched.

(9) Surface roughness The light diffusion film preferably has an arithmetic mean height Ra of 10 µm or less, more preferably 5 µm or less, even more preferably 3 µm or less, and preferably 1 µm or less. Even more preferable. On the other hand, the lower limit of the arithmetic mean roughness Ra is not particularly limited. More preferred.
When the arithmetic mean height Ra is within the above range, when the present light diffusion film is mounted on a display, air bubbles are less likely to occur between the film and the adhesive layer interface. In addition, when the present light diffusion film is used as a wound body, the handleability is improved.
The arithmetic mean height Ra in the present invention can be measured according to JIS B0601:2001 by the method described in Examples.

(10) Tensile strength When the present light diffusion film has a structure containing a dispersed component, the tensile strength ratio (σ _MD /σ _TD ) in the MD direction and the TD direction is preferably 0.75 to 1.25, especially It is more preferably 0.80 or more and 1.20 or less, more preferably 0.85 or more and 1.15 or less, and more preferably 0.90 or more and 1.10 or less. preferable.
When the tensile strength ratio (σ _MD /σ _TD ) in the MD direction and the TD direction is within the above range, the anisotropy of the tensile strength is small. This means that it is difficult for Therefore, when the tensile strength ratio (σ _MD /σ _TD ) in the MD direction and the TD direction is within the above range, reflection due to interfacial separation between the matrix component and the dispersion component occurs in both the MD direction and the TD direction. The film tends to have low reflectivity and high total light transmittance.
In the present invention, the "MD direction" indicates the take-up (flow) direction of the sheet or film when manufacturing the sheet or film, and the "TD direction" indicates the orthogonal direction.

When the present light diffusion film has a structure containing a dispersed component, both the tensile strength σMD in the _MD direction and the tensile strength _σTD in the TD direction are preferably 50 MPa or more, more preferably 55 MPa or more, and 60 MPa or more. is more preferable. On the other hand, although the upper limit of the tensile strength is not particularly limited, it is preferably 200 MPa or less.
When the tensile strength _σMD in the MD direction and the tensile strength _σTD in the TD direction are within the above ranges, it means that interfacial separation between the matrix component and the dispersed component in the film is unlikely to occur. Therefore, when the tensile strength σMD in the _MD direction and the tensile strength _σTD in the TD direction are within the above ranges, reflection due to interfacial peeling between the matrix component and the dispersed component is less likely to occur, and the film tends to have low reflectivity. , the total light transmittance tends to be high.

The tensile strength of the light diffusion film can be measured according to JIS K7161-1 by the method described in Examples.

<First layer>
The first layer will be described below. The first layer has a structure capable of scattering incident light in the traveling direction of the light.

As the light diffusion film, a liquid crystal component, organic fine particles, anisotropic inorganic filler, or other dispersing component is added to the matrix resin (for example, the above-mentioned Patent Document 1, JP-A-2010-079197, International Publication No. 2015/182517, etc. ); those having an uneven structure on the film surface (for example, JP-A-2013-114846, etc.); It has been known.
It is difficult to improve the anisotropic light diffusibility of a light diffusion film in which a dispersing component such as a liquid crystal component, organic fine particles, or an anisotropic inorganic filler is added to a matrix resin, because it is difficult to control the aspect ratio of the dispersing component. It is considered difficult to keep the luminance ratio/front luminance ratio within the above range.
A light diffusion film having an uneven structure on its surface can have a 60° luminance ratio/front luminance ratio within the above range by adjusting the uneven structure. However, such a light diffusion film may cause a striped pattern called moire when mounted on a display, and it may be difficult to increase the production speed due to the manufacturing method.
A light diffusion film having a sea-island structure with a continuous phase (I) and a dispersed phase (II) has a 60° luminance ratio by adjusting the components and amounts of the continuous phase (I) and the dispersed phase (II). /front luminance ratio can be set within the above range. It is considered that such a light diffusion film causes less moiré and has good productivity.
From the above viewpoints, the first layer preferably has an uneven structure on the surface or has a sea-island structure with the continuous phase (I) and the dispersed phase (II), and the continuous phase (I) and the dispersed phase (II) It is more preferable to have a sea-island structure by Preferred forms of the first layer are described below.

1. First Embodiment A first layer according to a first preferred embodiment of the present invention has an uneven structure on its surface.
The concave-convex structure of the first layer is not particularly limited as long as the 60° luminance ratio/front luminance ratio of the present light diffusion film is within the above range. Examples of the first layer having an uneven structure on its surface include the following.
(1) Concavities and convexities are formed on the surface of a mold base material made of metal, resin, etc., and the shape is transferred from this mold to a resin film, etc. JP 2008-302591, JP 2012-063670, JP 2015-004857, etc.)
(2) Laminated sheet having a prism shape on a transparent substrate (for example, JP-A-2006-059542, etc.)
(3) Those having a coating layer containing organic beads on the surface (for example, JP-A-2003-202416, etc.)
(4) A resin layer patterned by printing or the like and heat-treated (for example, JP-A-2000-105550, etc.)
(5) Sandblasted or etched resin layer (for example, JP-A-2000-105550, JP-A-2016-051116, etc.)
In the above (1) to (5), if anisotropy is given to the distance between the irregularities and the height of the protrusions, the anisotropic light diffusion property can be imparted to the film, and the 60 ° luminance ratio / front luminance ratio is within the above range. can do.

2. Second Embodiment A first layer according to a second preferred embodiment of the present invention has a sea-island structure with a continuous phase (I) and a dispersed phase (II).
The continuous phase (I) is the phase that forms the sea in the island-sea structure, and the dispersed phase (II) is the phase that forms the islands in the island-sea structure.
In order to distinguish between the continuous phase and the dispersed phase, the dispersed structure can be observed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM).

The first layer has a dispersed structure in which the island portions of the sea-island structure, ie, the dispersed phase (II), are extended in the MD direction, and the sea portion, ie, the continuous phase (I) is dispersed. preferable. By having such a dispersion structure, the anisotropic light diffusibility of the film is enhanced.

At least one of the continuous phase (I) and the dispersed phase (II) of the first layer preferably contains a thermoplastic resin having an average refractive index of 1.53 or less.
The average refractive index of the thermoplastic resin is more preferably 1.52 or less, even more preferably 1.51 or less. On the other hand, although the lower limit of the average refractive index is not particularly limited, it is preferably 1.45 or more.
When at least one of the continuous phase (I) and the dispersed phase (II) contains a thermoplastic resin having an average refractive index within the above range, the internal reflection of the film is suppressed and the reflectivity tends to be low. In addition, since the refractive index difference with a general adhesive layer is unlikely to increase, interfacial reflection with the adhesive layer can also be suppressed.

The thermoplastic resin having an average refractive index of 1.53 or less is preferably a resin component that constitutes the continuous phase (I).
Among them, it is preferable that the thermoplastic resin having an average refractive index of 1.53 or less accounts for 50% by mass or more of the resin components constituting the continuous phase (I). Among them, it accounts for 80% by mass or more, more preferably 90% by mass or more (including 100% by mass).

Further, the refractive index difference between the continuous phase (I) and the dispersed phase (II) is preferably 0.010 to 0.080, more preferably 0.015 or more or 0.075 or less, and more preferably 0.020 or more or 0.070 or less is more preferable.
When the refractive index difference between the continuous phase (I) and the dispersed phase (II) is within the above range, the internal reflection of the film is suppressed and the reflectivity tends to be low. In addition, the anisotropic light diffusibility can be enhanced while maintaining a high total light transmittance.
The refractive index difference between the continuous phase (I) and the dispersed phase (II) is calculated as the absolute value of the refractive index difference between the raw material resins forming the continuous phase (I) and the dispersed phase (II).
In addition, when two or more raw material resins form each phase of the continuous phase (I) or the dispersed phase (II), the refractive index of each phase can be determined from the compounding ratio of the raw material resins and the average refractive index of each resin. shall be calculated.

[Continuous Phase (I) and Dispersed Phase (II)]
The continuous phase (I) and dispersed phase (II) in the first layer can be formed by using at least two thermoplastic resins.
Examples of the thermoplastic resin include polyester resins such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate and polybutylene terephthalate; polyolefins such as polyethylene, polypropylene, cyclopolyolefin and polymethylpentene; acetylcellulose and nitrocellulose. Cellulose derivatives such as , acetylbutyl cellulose, ethyl cellulose, methyl cellulose; vinyl resins such as vinyl acetate and its copolymers, vinyl chloride and its copolymers, vinylidene chloride and its copolymers; acetals such as polyvinyl formal and polyvinyl butyral Acrylic resins such as acrylic resins such as polyacrylates and copolymers thereof, methacrylic resins such as polymethacrylates and copolymers thereof; acrylic resins such as polystyrene resins; polyamide resins; be able to.

It is preferable that one of the above thermoplastic resins is a thermoplastic resin having an average refractive index of 1.53 or less (also referred to as "resin α").
More specifically, the at least two thermoplastic resins include a combination of resin α and a thermoplastic resin incompatible therewith (also referred to as “resin β”).
The term "incompatible" means a state in which at least two resin components are not completely mixed, and may be partially mixed. (TEM) or scanning electron microscope (SEM), micro-phase separation structure due to sea-island structure is observed.

By forming the continuous phase (I) and the dispersed phase (II) with materials containing these two types of resins α and β, the vicinity of the direction inclined 60° from the normal N direction of the surface of the light diffusion film to the light diffusion direction An ideal island component having strong diffusivity can be formed, and an optimum dispersion structure can be formed to exhibit excellent anisotropic light diffusibility.

In addition, the first layer may contain a resin γ as a third component in addition to the resins α and β. The resin γ is a thermoplastic resin incompatible with the resin α, and preferably forms the dispersed phase (II) together with the resin β and is compatible with or phase-separated from the resin β in the dispersed phase (II). By containing the resin γ, the anisotropic light diffusibility of the present light diffusion film can be adjusted.

The resin α, resin β, and resin γ will be described in detail below.

[Resin α]
Examples of the resin α having an average refractive index of 1.53 or less include polymethyl methacrylate, polypropylene, polyurethane, and the like. From the viewpoint of above, a polycarbonate resin containing a structural unit (a) derived from a dihydroxy compound represented by general formula (1) is preferred. The polycarbonate resin containing the structural unit (a) is preferably the main component in the continuous phase (I) of the first layer.
In the present invention, the "main component" means the resin with the highest content among the resins constituting the continuous phase (I) or the dispersed phase (II), for example, the continuous phase (I) or the dispersed phase (II ), a resin component that accounts for 50% by mass or more, particularly 70% by mass or more, especially 80% by mass or more (including 100% by mass).

Examples of the dihydroxy compound represented by the general formula (1) include isosorbide, isomannide and isoide, which are stereoisomers. These may be used individually by 1 type, and may be used in combination of 2 or more type.
Since these dihydroxy compounds do not have a phenolic hydroxyl group, they are usually produced by transesterification using diester carbonate.

Among these dihydroxy compounds, isosorbide, which is obtained by dehydration condensation of sorbitol produced from various easily available starches, which exists abundantly as a plant-derived resource, has transparency, stretchability, heat resistance and It is most preferable from the aspect of anisotropic light diffusion.

The structural unit (a) in the polycarbonate resin accounts for preferably 35 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more of all structural units derived from the dihydroxy compound. Also, it is preferably 90 mol % or less, more preferably 85 mol % or less, and still more preferably 80 mol % or less.
If the ratio of the structural unit (a) is at least the above lower limit, it becomes easy to increase the molecular weight of the polycarbonate resin. On the other hand, if the said ratio is below the said upper limit, polycarbonate resin will be hard to color.

The polycarbonate resin containing the structural unit (a) may further contain a structural unit (b) derived from a dihydroxy compound other than the structural unit (a).

Examples of the structural unit (b) include a structural unit (b1) derived from an aliphatic dihydroxy compound and/or a structural unit (b2) derived from an alicyclic dihydroxy compound.
Specific examples of the aliphatic dihydroxy compound and the alicyclic dihydroxy compound include the following.

(Aliphatic dihydroxy compound)
Examples of the aliphatic dihydroxy compound include 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-ethyl -1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, hydrogenated dilinoleyl glycol, hydrogenated dioleyl glycol, etc. are mentioned.
These aliphatic dihydroxy compounds may be used singly or in combination of two or more.

The molar ratio between the structural unit (a) and the structural unit (b1) derived from the aliphatic dihydroxy compound can be selected at any ratio. Flexibility and moldability can be improved by adjusting the molar ratio.
Therefore, from such a viewpoint, the molar ratio of the structural unit (a) and the structural unit (b1) derived from the aliphatic dihydroxy compound is preferably 35:65 to 99:1, and 40:60 to More preferably 90:10, even more preferably 45:55 to 80:20.

(Alicyclic dihydroxy compound)
Alicyclic dihydroxy compounds include compounds containing a 5- or 6-membered ring structure. When the alicyclic dihydroxy compound has a 5-membered ring structure or a 6-membered ring structure, there are advantages such as improved heat resistance.
The six-membered ring structure may be fixed in a chair or boat shape by a covalent bond.
The number of carbon atoms contained in the alicyclic dihydroxy compound is usually 70 or less, preferably 50 or less, more preferably 30 or less. An alicyclic dihydroxy compound having 70 or less carbon atoms is preferred because it is easy to synthesize and purify, and is inexpensive and readily available.

Specific examples of the alicyclic dihydroxy compound containing a 5-membered ring structure or 6-membered ring structure include alicyclic dihydroxy compounds represented by the following general formula (2) or (3).
HOCH ₂ —R ₉ —CH ₂ OH (2)
HO—R ₁₀ —OH (3)
(In general formulas (2) and (3), R ₉ and R ₁₀ each independently represent a substituted or unsubstituted divalent group containing a cycloalkyl structure having 4 to 20 carbon atoms.)

Examples of the alicyclic dihydroxy compound represented by the general formula (2) include cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, decalindimethanol, tricyclotetradecanedimethanol, norbornanedimethanol, and adamantanediethanol. Methanol etc. are mentioned.

The alicyclic dihydroxy compounds represented by the general formula (3) include tricyclodecanediol, pentacyclopentadecanediol, decalindiol, tricyclotetradecanediol, norbornanediol, and adamantanediol.

These alicyclic dihydroxy compounds may be used singly or in combination of two or more.

The structural unit (b3) is any one or more selected from cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol and pentacyclopentadecanedimethanol from the viewpoint of availability and ease of handling. Structural units derived from compounds are particularly preferred.

The molar ratio of the structural unit (a) and the structural unit (b2) derived from the alicyclic dihydroxy compound is preferably 35:65 to 99:1, more preferably 40:60 to 90:10. More preferably, it is 45:55 to 80:20.
When the molar ratio is within the above range, the polycarbonate resin is less likely to be colored and the molecular weight can be easily increased.

(Glass transition temperature (Tg) of resin α)
From the viewpoint of heat resistance, the glass transition temperature (Tg) of the resin α is preferably 90° C. or higher, more preferably 100° C. or higher, and more preferably 110° C. or higher. On the other hand, from the viewpoint of moldability, the temperature is preferably 350° C. or lower, more preferably 300° C. or lower, and more preferably 250° C. or lower.
In the present invention, the glass transition temperature of the resin is determined according to JIS K7121:2012 using a differential scanning calorimeter (for example, "DSC8500" manufactured by PerkinElmer Japan Co., Ltd.) with a temperature range of 0 to 200 ° C. and a heating rate of A value measured at 10°C/min.

(Apparent viscosity of resin α η _240,α )
The apparent viscosity η _240,α of the resin α at 240° C. and a shear rate of 100 (1/s) is preferably 100 (Pa s) to 10000 (Pa s), especially 200 (Pa s) from the viewpoint of moldability. (Pa·s) or more and 5000 (Pa·s) or less is more preferable, and among them, 300 (Pa·s) or more and 1000 (Pa·s) or less is more preferable.

(Content of resin α)
The content of resin α in the first layer is preferably 10 to 90% by mass, more preferably 20% by mass or more or 80% by mass or less, and more preferably 30% by mass or more or 70% by mass or less. Among them, 40% by mass or more or 65% by mass or less is more preferable.
When the content of the resin α is within the above range, the dispersed phase (II) is appropriately formed in the first layer, and the anisotropic light diffusibility is improved.

[Resin β]
Examples of the resin β include at least one resin selected from the group consisting of amorphous polyester resins and amorphous styrene resins. The resin β is preferably the main component in the dispersed phase (II) of the first layer.

(amorphous polyester resin)
As the amorphous polyester resin, for example, a polyalkylene terephthalate resin such as polyethylene terephthalate or a polyalkylene-2,6-naphthalate resin such as polyethylene-2,6-naphthalate is acid-modified and/or diol-modified. A crystalline copolyester may be mentioned. Among them, from the viewpoint of optimizing the dispersion structure, an amorphous polyester resin modified with a diol component having an alicyclic structure, that is, an amorphous polyester resin containing a diol component having an alicyclic structure is preferred.
In addition, "amorphous" means having no melting peak in DSC measurement.

In addition, among others, from the viewpoint of optimizing the dispersion structure, a diol component having at least one alicyclic structure selected from spiroglycol, isosorbide, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol Amorphous polyester resins containing are particularly preferred.
As the amorphous polyester resin containing a diol component having an alicyclic structure, various commercially available raw materials can be preferably used. manufactured by EASTMAN Chemical Co., Ltd., using spiroglycol), trade name: "TRITAN (registered trademark)" (manufactured by EASTMAN Chemical Co., Ltd., using 2,2,4,4-tetramethyl-1,3-cyclobutanediol), and commercial products Name: "ECOZEN (registered trademark)" (manufactured by SK Chemicals, using isosorbide).

(amorphous styrene resin)
Examples of the amorphous styrene resin include styrene resin, acrylonitrile/styrene copolymer (AS resin), and acrylonitrile/butadiene/styrene copolymer (ABS resin).

(Average refractive index of resin β)
The average refractive index of the resin β is preferably 1.53 or higher, more preferably 1.54 or higher, and even more preferably 1.55 or higher, from the viewpoint of anisotropic light diffusion and low reflectivity. On the other hand, from the viewpoint of low reflectivity, it is preferably 1.60 or less, more preferably 1.58 or less.

(Glass transition temperature (Tg) of resin β)
From the viewpoint of heat resistance, the glass transition temperature (Tg) of the resin β is preferably 70° C. or higher, more preferably 80° C. or higher, and more preferably 90° C. or higher. On the other hand, from the viewpoint of moldability, the temperature is preferably 350° C. or lower, more preferably 300° C. or lower, and more preferably 250° C. or lower.

(Apparent viscosity η _240, β of resin β)
The apparent viscosity η _240,β of the resin β at a shear rate of 100 (1/s) at 240° C. is preferably higher than the apparent viscosity η _240,α of the resin α. , preferably 400 (Pa s) to 10000 (Pa s), more preferably 600 (Pa s) or more or 9000 (Pa s) or less, among which 800 (Pa s) ) or more or 8000 (Pa·s) or less.

[Resin γ]
Examples of the resin γ include at least one selected from the amorphous polyester resins exemplified for the resin β and the polycarbonate resins other than those exemplified for the resin α.

The polycarbonate resin as the resin γ is not particularly limited as long as it is a polymer compound having a carbonate ester bond (-O-(C=O)-O-) in its main chain. Examples thereof include 4,4'-dioxydiarylalkane-based polycarbonates such as 2,2-bis(4-hydroxyphenyl)propane-based polycarbonates (bisphenol A-based polycarbonates).

When the first layer contains the resin γ as the third component, preferred embodiments of the resins β and γ include the following combinations, and these resins β and γ preferably constitute the dispersed phase (II).
(1) Resins β and γ are both amorphous polyester resins. That is, the first layer contains two or more amorphous polyester resins.
(2) The resin β is an amorphous polyester resin, and the resin γ is a polycarbonate resin other than those exemplified for the resin α. That is, the first layer contains an amorphous polyester resin and a polycarbonate resin (excluding the polycarbonate resin containing the structural unit (a)).

In the case of (1) above, resin β (the resin with the higher content among the amorphous polyester resins in the dispersed phase (II)) and resin γ (among the amorphous polyester resins in the dispersed phase (II) The content mass ratio of the resin having a smaller content is preferably 50:50 to 95:5, more preferably 50:50 to 90:10, further preferably 50:50 to 85:15, and 50:50 to 80 :20 is even more preferred.

In the case of (2) above, the content mass ratio of the resin β and the resin γ is preferably 50:50 to 95:5, more preferably 50:50 to 90:10, further preferably 50:50 to 85:15. :50 to 80:20 is even more preferable.

(Average refractive index of resin γ)
The average refractive index of the resin γ is preferably higher than that of the resin β. Even more preferable. On the other hand, from the viewpoint of low reflectivity, it is preferably 1.64 or less, more preferably 1.62 or less, and even more preferably 1.60 or less.

(Glass transition temperature (Tg) of resin γ)
From the viewpoint of heat resistance, the glass transition temperature (Tg) of resin γ is preferably 70° C. or higher, more preferably 80° C. or higher, and more preferably 90° C. or higher. On the other hand, from the viewpoint of moldability, the temperature is preferably 350° C. or lower, more preferably 300° C. or lower, and more preferably 250° C. or lower.

(Apparent viscosity η _240, γ of resin γ)
The apparent viscosity η _240,γ of the resin γ at a shear rate of 100 (1/s) at 240° C. is preferably higher than the apparent viscosity η _240,β of the resin β. , preferably 400 (Pa s) to 10000 (Pa s), more preferably 600 (Pa s) or more or 9000 (Pa s) or less, among which 800 (Pa s) ) or more or 8000 (Pa·s) or less.

[Dispersed phase volume and dispersion diameter]
The dispersed phase volume of the first layer is preferably 20 μm ³ or more, more preferably 30 μm ³ or more, and even more preferably 40 μm ³ or more at the central portion in the thickness direction. Among them, it is preferably 50 μm ³ or more, more preferably 60 μm ³ or more, and even more preferably 70 μm ³ or more. Also, it is preferably 120 μm ³ or less, more preferably 110 μm ³ or less, even more preferably 100 μm ³ or less, and even more preferably 90 μm ³ or less.
When the volume of the dispersed phase in the first layer is equal to or greater than the above lower limit, the dispersed diameters in the TD direction and the thickness direction are appropriately large, so that the reflection per dispersed phase can be reduced. In addition, since the dispersion diameter in the MD direction is moderately large, the anisotropic light diffusibility is also improved. On the other hand, when the dispersed phase volume is equal to or less than the above upper limit, the dispersion diameter in the TD direction and the thickness direction does not become too large, so the vicinity of the direction inclined 60° from the normal N direction of the light diffusion film surface to the light diffusion direction. An ideal island component with strong diffusivity can be formed, and an optimum dispersion structure can be obtained to enhance the anisotropic light diffusibility.

From the same point of view, the dispersed phase volume of the first layer is preferably 10 μm ³ or more, more preferably 15 μm ³ or more, and 20 μm in the surface layer and/or back layer in the thickness direction. More preferably, it is ³ or more. Among them, it is preferably 25 μm ³ or more, more preferably 30 μm ³ or more, and even more preferably 35 μm ³ or more. Also, it is preferably 120 μm ³ or less, more preferably 110 μm ³ or less, even more preferably 100 μm ³ or less, and even more preferably 90 μm ³ or less.

The dispersed phase volume was calculated by calculating the average dispersed diameter in the MD direction, the average dispersed diameter in the TD direction, and the average dispersed diameter in the thickness direction by the method described later, and assuming that the dispersed phase (II) was elliptical. value.

In the present invention, the “central portion in the thickness direction” refers to an area corresponding to ±15% of the thickness of the light diffusion film from the center in the thickness direction of the light diffusion film, and the “surface layer and / or back in the thickness direction "Layer portion" refers to a region corresponding to 35% of the thickness of the light diffusion film from the front surface or back surface in the thickness direction of the light diffusion film.

The dispersed phase area in the TD cross section of the first layer is preferably 2 μm ² or more, more preferably 2.5 μm ² or more, and even more preferably 3 μm ² or more at the central portion in the thickness direction. . Among them, it is preferably 3.5 μm ² or more, more preferably 4 μm ² or more. Also, it is preferably 100 μm ² or less, more preferably 80 μm ² or less, even more preferably 50 μm ² or less, and even more preferably 30 μm ² or less.
When the dispersed phase area in the TD cross section of the first layer is at least the above lower limit, the dispersion diameters in the TD direction and the thickness direction are appropriately large, so that the reflection per dispersed phase can be reduced. On the other hand, when the dispersed phase area in the TD cross section is equal to or less than the above upper limit, the dispersion diameter in the TD direction and the thickness direction does not become too large, so the light diffusion film is tilted at 60° from the normal N direction of the surface of the light diffusion film to the light diffusion direction. An ideal island component with strong diffusivity can be formed in the vicinity of the polar direction, and an optimum dispersion structure can be obtained to enhance the anisotropic light diffusibility.

From the same point of view, the dispersed phase area in the TD cross section of the first layer is preferably 1 μm ² or more, more preferably 1.5 μm ² or more in the surface layer portion and/or the back layer portion in the thickness direction. is more preferable, and 2 μm ² or more is even more preferable. Among them, it is preferably 2.5 μm ² or more, more preferably 3 μm ² or more, still more preferably 3.5 μm ² or more, and even more preferably 4 μm ² or more. Also, it is preferably 100 μm ² or less, more preferably 80 μm ² or less, even more preferably 50 μm ² or less, and even more preferably 30 μm ² or less.

The dispersed phase area is calculated by calculating the average dispersion diameter in the TD direction and the average dispersion diameter in the thickness direction in the TD cross section of the present light diffusion film by the method described later, and assuming that the dispersed phase (II) is elliptical. is the value
In the present invention, the term “TD cross section” refers to a cross section obtained by cutting the present light diffusion film in the TD direction at the center of the MD direction and having sides in the TD direction and the thickness direction of the film as shown in FIG. .
Further, in the present invention, the term "MD cross section" refers to a cross section in which the present light diffusion film is cut in the MD direction at the center of the TD direction, and as shown in FIG. Say.

The light diffusion film preferably has a dispersed structure in which the island portions of the sea-island structure in the first layer extend in the MD direction and are dispersed in the sea portions. From this point of view, the ratio of the average dispersion diameter in the MD direction to the average dispersion diameter in the TD direction of the dispersed phase (II) (MD average dispersion diameter / TD average dispersion diameter) is the central part in the thickness direction and the surface part in the thickness direction and/or in the back layer, it is preferably 1.1 or more and 120 or less, more preferably 2 or more or 60 or less, more preferably 3 or more or 30 or less, especially 5 or more Alternatively, it is more preferably 25 or less.

In the first layer, from the viewpoint of forming the ideal island component and obtaining an optimum dispersed structure, the size of the dispersed component (dispersed phase (II)) in the MD direction of the film, that is, the average dispersion diameter in the MD direction is preferably 3 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, even more preferably 15 μm or more, and 20 μm or more at the central portion in the thickness direction. is particularly preferred.
On the other hand, from the viewpoint of morphology control, it is preferably 60 μm or less.

In addition, the average dispersion diameter in the MD direction is preferably 1.5 μm or more, more preferably 2.5 μm or more, and is preferably 5 μm or more in the surface layer portion and/or the back layer portion in the thickness direction. More preferably, it is 10 μm or more, even more preferably 15 μm or more.
On the other hand, from the viewpoint of morphology control, it is preferably 60 μm or less.

Furthermore, from the same point of view, the average dispersion diameter in the direction perpendicular to the MD direction (TD direction) of the film is preferably 0.5 to 10 μm at the central portion in the thickness direction, especially 0.8 μm or more or 7 μm. It is more preferably 1 μm or more or 5 μm or less.
In addition, the average dispersion diameter in the TD direction is preferably 0.4 to 10 μm, more preferably 0.5 μm or more or 7 μm or less in the surface layer and / or back layer in the thickness direction. Among them, it is more preferably 0.6 μm or more or 5 μm or less.

Furthermore, from the same viewpoint, the average dispersion diameter in the thickness direction of the film is preferably 0.1 to 10 μm, more preferably 0.5 μm or more or 7 μm or less, at the central portion in the thickness direction. Among them, the thickness is more preferably 1 μm or more or 5 μm or less.
In addition, the average dispersion diameter in the thickness direction of the film is preferably 0.1 to 10 μm, more preferably 0.2 μm or more or 7 μm or less, in the surface layer portion and/or the back layer portion in the thickness direction. Among them, the thickness is more preferably 0.3 μm or more or 5 μm or less.

Any of the above average dispersion diameters can be obtained by photographing the cross section of the corresponding portion with a transmission electron microscope (TEM) or scanning electron microscope (SEM), and measuring the dispersion diameter in the photographing range using the free software "ImageJ". It is a value calculated as an average of all dispersion diameters within a range that can be analyzed and confirmed. The photographing range may be appropriately adjusted depending on the size of the dispersed phase (II), but is preferably a range in which 10 or more dispersed phases (II) can be observed.

In order to adjust the size of the dispersed phase (II) in the first layer as described above, in the manufacturing method, for example, the discharge amount Q (kg / h) and the screw rotation speed N (rpm) In addition to means for adjusting the ratio Q/N (kg/h/rpm), it is also effective to adjust the viscosity difference between the resins α and β forming the first layer. However, it is not limited to these methods.

From this point of view, the apparent viscosity ratio η _240,β / _240, α of the resins α and β forming the first layer at 240°C and a shear rate of 100 (1/s) is 1.5 to 15. is preferably 1.8 or more or 10 or less, more preferably 2 or more or 5 or less.

<Second layer>
The light diffusion film may have a second layer on at least one surface of the first layer.
When the first layer has an uneven structure on the surface, the provision of the second layer can suppress damage to other layers.
In addition, when the first layer has a sea-island structure consisting of the continuous phase (I) and the dispersed phase (II), shear stress is generally likely to be applied to the front and back layers during film formation. The dispersion diameter of the surface layer portion and/or the back layer portion tends to be small. Therefore, since the present light diffusion film includes the second layer, the shear stress applied to the front and back sides of the first layer during film production can be reduced, so that the dispersed phase (II) on the front and back sides of the first layer The dispersion diameter can be increased, and both excellent anisotropic light diffusibility and low reflectivity can be achieved.

The second layer preferably has a continuous phase (Ib) composed of at least one selected from the thermoplastic resins exemplified for the first layer.
The term "continuous phase (Ib)" means a phase in which individual domains are connected without isolation from a macroscopic point of view, but it does not matter if there is a part that is not connected.

Further, the continuous phase (Ib) of the second layer is preferably formed from a resin having an average refractive index of 1.45 to 1.53. More preferably, it is formed from a resin having a viscosity of 1.51 or more.
By forming the continuous phase (Ib) with the above resin, even when another member is laminated on the second layer via an adhesive layer made of an acrylic adhesive, the second layer and the corresponding Reflection at the interface with the adhesive layer can be suppressed.

The continuous phase (Ib) contained in the second layer is preferably formed from a resin having a glass transition temperature of 90° C. or higher from the viewpoint of enhancing the heat resistance of the present light diffusion film.
From this point of view, the glass transition temperature of the resin constituting the continuous phase (Ib) contained in the second layer is preferably 90° C. or higher, more preferably 100° C. or higher, and more preferably 110° C. or higher. is more preferable, and 120° C. or higher is even more preferable. On the other hand, from the viewpoint of moldability, the temperature is preferably 350° C. or lower, more preferably 300° C. or lower, and even more preferably 250° C. or lower.

From the viewpoint of increasing the surface hardness of the light diffusion film, the second layer preferably has a surface hardness of HB or higher, more preferably F or higher.
In order to increase the surface hardness of the second layer, it is preferable to employ a resin having high hardness as the main component resin constituting the second layer. However, it is not limited to this method.

Considering the average refractive index, the continuous phase (Ib) of the second layer is preferably formed from a polycarbonate resin or polymethyl methacrylate containing the structural unit (a) derived from the dihydroxy compound.
Among them, from the viewpoint of transparency, stretchability, heat resistance, low reflectivity, anisotropic light diffusibility, realization of high hardness, etc., it is preferable to form a polycarbonate resin containing the structural unit (a) derived from the above dihydroxy compound. Especially preferred. Among these, a resin containing 50 mol% or more of the structural unit (a) derived from a dihydroxy compound is particularly preferable, and a resin containing 55 mol% or more of the structural unit (a) is more preferable, and a resin containing 60 mol% or more of the structural unit (a). is more preferred.

More preferably, the continuous phase (Ib) of the second layer contains the same thermoplastic resin as the thermoplastic resin forming the continuous phase (I) of the first layer. When the first layer has a sea-island structure with the continuous phase (I) and the dispersed phase (II), the composition of the resin constituting the continuous phase (I) of the first layer and the continuous phase (Ib) of the second layer When the resin is of the same type, reflection is less likely to occur at the interface between the first layer and the second layer, so that both excellent anisotropic light diffusion and low reflectivity can be achieved.
The term "thermoplastic resin of the same type as the thermoplastic resin forming the continuous phase (I) of the first layer" means that a polymer composed of the same or similar monomers is used as the base resin.
In this case, the monomers constituting the main repeating units of the thermoplastic resin component may be the same or of the same type, including the case where the degrees of polymerization are different.
In addition, in the case of having a copolymerizable monomer, in addition to the case where the monomer ratio is different, it includes the case where the copolymerizable monomer is different, and also includes the case where the degree of polymerization is different as described above. .

From the viewpoint of reflectance, the second layer preferably does not substantially have a dispersed phase, particularly a dispersed phase having a refractive index different from that of the continuous phase (Ib).
The phrase “substantially does not have a dispersed phase having a refractive index different from that of the continuous phase (Ib)” means that the cross-sectional area of the second layer in the TD direction (total area including the continuous phase and the dispersed phase) is It means that the area ratio of the phase (Ib) and the dispersed phase having a different refractive index is 20 area% or less, more preferably 10 area% or less, and most preferably 5 area% or less. It means that there is
The dispersed phase having the same refractive index as that of the continuous phase (Ib) travels straight at the interface between the continuous phase (Ib) and the dispersed phase, so there is no risk that the reflectance will increase. can.

The second layer is laminated on at least one side of the first layer, e.g. Adjacent lamination is particularly preferred.
In this specification, the terms “upper side” and “upper side” refer to the surface that was in contact with the cast surface, and the terms “lower side” and “lower side” refer to the side that was in contact with the cast surface. indicates the opposite surface.
In addition, the present light diffusion film can be used so that either the upper surface side (upper side) or the lower surface side (lower side) is arranged on the display surface side (viewing side), and the display It can be used so that either the upper surface side (upper side) or the lower surface side (lower side) is arranged on the surface side opposite to the surface side (viewing side).
In other words, the present light diffusion film can be used without distinguishing between the upper surface side (upper side) and the lower surface side (lower side).

The present light diffusion film is usually used by laminating with an adhesive layer, but when the second layer is provided, the interface between the adhesive layer and the first layer having a dispersed phase with a high refractive index is eliminated. and the reflectance can be reduced.

<Preferred embodiment>
Any one of the following aspects is more preferable for the present light diffusion film.
- Having at least a first layer capable of scattering incident light in the direction of travel of the light, and having a ratio of the 60° brightness ratio to the front brightness ratio (60° brightness ratio/front brightness ratio) of 0.30 or more and 0.60 It is below.
- Having at least a first layer capable of scattering incident light in the direction of travel of the light, and having a ratio of the 60° brightness ratio to the front brightness ratio (60° brightness ratio/front brightness ratio) of 0.30 or more and 0.50 It is below.
・Equipped with a first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), a haze measured in accordance with JIS K7136 of 40% or more, and a tensile strength ratio in the MD direction and the TD direction (σ _MD /σ _TD ) is 0.75 to 1.25.
・Equipped with a first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), a haze measured in accordance with JIS K7136 of 40% or more, and tensile strength in the MD direction σ _MD and TD All of them have a directional tensile strength σ _TD of 50 MPa or more.
- comprising a first layer having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II), wherein the dispersed phase volume at the central portion in the thickness direction of the first layer is 20 µm ³ or more and 120 µm ³ or less; The ratio of the average dispersion diameter in the MD to the average dispersion diameter in the TD of the phase (II) (MD average dispersion diameter/TD average dispersion diameter) is 3 or more at the central portion in the thickness direction.
- comprising a first layer having a sea-island structure composed of a continuous phase (I) and a dispersed phase (II), wherein the dispersed phase volume at the central portion in the thickness direction of the first layer is 20 µm ³ or more and 120 µm ³ or less; The area of the dispersed diameter in the TD cross section at the central portion in the thickness direction of the phase (II) is 2 μm ² or more.
- It has a sea-island structure with a continuous phase (I) and a dispersed phase (II), and at least one of the continuous phase (I) and the dispersed phase (II) contains a thermoplastic resin having an average refractive index of 1.53 or less.
- having a laminated structure comprising at least a first layer and a second layer, the first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), and the second layer , a continuous phase (Ib) laminated on at least one surface side of the first layer and containing the same thermoplastic resin as the thermoplastic resin forming the continuous phase (I) of the first layer .
- having a laminated structure comprising at least a first layer and a second layer, the first layer having a sea-island structure with a continuous phase (I) and a dispersed phase (II), and the second layer , which is laminated on at least one side of the first layer, has a continuous phase (Ib) containing a resin having a glass transition temperature of 90° C. or higher, and has a surface hardness of HB or higher.

<Structure of the present light diffusion film>
The present light diffusion film may have a single layer structure consisting of only the first layer, or may have a multilayer structure including the first layer and the second layer. When it has a multilayer structure, it may have other layers in addition to the first layer and the second layer.
Examples of the multilayer structure include, for example, a second layer/first layer, two types of two layers, a second layer/first layer/second layer, a first layer/second layer/ Two kinds of three layers of the first layer; hard coat layer / second layer / first layer, second layer / first layer / hard coat layer, adhesive layer / second layer / first layer layer, second layer/first layer/adhesive layer 3 types 3 layers; hard coat layer/second layer/first layer/hard coat layer, adhesive layer/second layer/first layer Layer/adhesive layer, hard coat layer/second layer/first layer/second layer, adhesive layer/second layer/first layer/second layer, hard coat layer/first layer / second layer / first layer, adhesive layer / first layer / second layer / first layer 3 types 4 layers; hard coat layer / second layer / first layer / second layer / hard coat layer, adhesive layer / second layer / first layer / second layer / adhesive layer, hard coat layer / first layer / second layer / first Layer/hard coat layer, adhesive layer/first layer/second layer/first layer/adhesive layer 3 types 5 layers; hard coat layer/second layer/first layer/adhesive 4 types of layers 4 layers, adhesive layer / second layer / first layer / second layer / hard coat layer, adhesive layer / first layer / second layer / first layer / hard Laminated structures, such as 4 types and 5 layers of a coat layer, are mentioned. In particular, the second layer/first layer/second layer two kinds three layers or hard coat layer/second layer/first layer/second layer, adhesive layer/second layer/ Four layers of three kinds of first layer/second layer are preferable.

Further, when the present light diffusion film has a multilayer structure, at least one layer may be a layer having anisotropic light diffusing properties, and the other layers may be layers having no anisotropic light diffusing properties. Further, all layers may be composed of an anisotropic light diffusion layer.
When a layer other than the anisotropic light diffusion layer is included, it is preferable that the anisotropic light diffusion layer serves as an intermediate layer.

The thickness of the first layer (each layer if multiple layers exist) is preferably 10 to 90% of the thickness of the entire light diffusion film, more preferably 20% or more or 80% or less. , more preferably 30% or more or 70% or less.
On the other hand, the thickness of the second layer (each layer if multiple layers exist) is preferably 5 to 90% of the thickness of the entire light diffusion film, especially 10% or more or 80% or less, especially 15% % or more or 70% or less.

In addition, in the present light diffusion film, the thickness ratio between the first layer and the second layer (second layer/first layer) is preferably in the range of 0.1 to 30, especially 0 It is more preferably in the range of 0.2 or more or 20 or less, more preferably in the range of 0.3 or more or 10 or less, and more preferably in the range of 0.4 or more or 5 or less. preferable.
When the first layer has a sea-island structure with the continuous phase (I) and the dispersed phase (II), by setting the thickness ratio of the first layer and the second layer to the above range, the first layer Since the shear stress applied to the front and back surfaces can be reduced, the dispersion diameter of the dispersed phase on the front and back surfaces of the first layer can be increased, and excellent anisotropic light diffusion and low reflectivity can be achieved.

The thickness of the light diffusion film is preferably 10-1000 μm. Above all, when the first layer has a sea-island structure with the continuous phase (I) and the dispersed phase (II), excellent anisotropic light can be obtained by setting the film thickness to be suitable for the dispersion structure formed in the present light diffusion film. From the viewpoint of obtaining diffusibility, it is preferably 15 to 500 μm, more preferably 20 μm or more or 300 μm or less, and even more preferably 25 μm or more or 100 μm or less.

<Form of the present light diffusion film>
The light diffusion film is preferably oriented in at least one direction.
When the first layer has a sea-island structure composed of the continuous phase (I) and the dispersed phase (II), as described above, it has a unique dispersed structure with island portions extending in the MD direction. It is preferred to have a dispersed structure in which the island portions are dispersed in the sea portion. In order to form such a dispersed structure, it is more preferable to be oriented in one direction.
The unidirectional orientation of the present light-diffusing film means that the island portions of the first layer are elongated in the MD direction in the cross-sectional view (MD cross-section) of the anisotropic light-diffusing film. You can check by checking.

<Method for producing the present light diffusion film>
When the first layer has an uneven structure on the surface, the methods (1) to (5) described in the above "1. First Embodiment" can be used as the method for producing the present light diffusion film.

When the first layer has a sea-island structure with the continuous phase (I) and the dispersed phase (II), the method for producing the present light diffusion film includes, for example, a mixed resin composition containing at least two thermoplastic resins, A method of forming a film by melting can be mentioned.
Examples of film-forming methods include a T-die casting method, a calendering method, and an inflation method.
Among these methods, the T die casting method is preferable from the viewpoint of film formation stability and production efficiency.
When the present light diffusion film has a multi-layer structure including a first layer and a second layer, a film insert method, a melt extrusion method, an extrusion lamination method, a heat press method, a solution casting method, etc., can be used. From the point of view, the melt extrusion method is particularly preferably used.
As the melt extrusion method, the resin compositions used for the first layer and the second layer are heated and melted in separate extruders, and laminated in a molten state by a method such as a coextrusion multilayer die method or a feed block method. After that, a co-extrusion method can be mentioned in which the mixture is formed into a film by inflation, T-die casting, or the like.

The extrusion temperature of the film is preferably in the range of approximately 220°C to 300°C, more preferably in the range of 230°C to 280°C, although it depends on the flow characteristics of each resin.
When the extrusion temperature is 220° C. or higher, the film can be sufficiently formed so that the molten resin can flow.

In addition, the ratio of the discharge amount Q (kg/h) and the screw rotation speed N (rpm); It is more preferably in the range of ~0.90.

Thus, by adjusting the extrusion temperature and the discharge rate Q within suitable ranges, the diameter of the resin forming the dispersed phase (II) in the mixed resin composition can be controlled.

The orientation direction may be either the take-off (flow) direction (MD) of the film or the direction perpendicular to the MD (TD). From the viewpoint of controlling the diameter of the dispersed resin in the T die casting method, it is preferable to orient in the MD.
That is, in the present light diffusion film, it is preferable that the axis (S axis) parallel to the orientation direction is MD, and the axis (P axis) perpendicular to the orientation direction and parallel to the film surface is TD. It will be.

Moreover, the method for orientation is not particularly limited. For example, by uniaxially stretching the sheet formed by the T die casting method as described above in the MD or TD, or by increasing the take-up speed (speed of the cast roll) when forming the film by the T die casting method. Examples include a method of applying a draft to the MD, and a method of applying a draft to the MD by increasing the take-up speed when forming a film by the inflation method.
Among them, the method of drafting the sheet formed by the T-die casting method as described above in the MD is preferable from the viewpoint of controlling the diameter of the dispersed resin.
The draft is a process of stretching in the MD direction at a casting speed during film production.

The stretching method is not particularly limited as long as it is stretched in at least one direction, and may be a method of monoaxial stretching in the MD or TD direction or a method of biaxial stretching in the MD and TD directions. may

<<Anisotropic light diffusion film with adhesive layer>>
The present light-diffusing film can be in a form in which an adhesive layer is provided on one side or both sides, that is, in the form of a so-called anisotropic light-diffusing film with an adhesive layer (referred to as "this anisotropic light-diffusing film with an adhesive layer"). . That is, the anisotropic light-diffusing film with an adhesive layer has an adhesive layer on at least one surface of the light-diffusing film.

The pressure-sensitive adhesive layer preferably contains at least one or more selected from rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, and vinyl-based pressure-sensitive adhesives. preferably included as Among them, it is preferable to contain an acrylic pressure-sensitive adhesive, and it is particularly preferable to contain it as a main component.
In this case, the main component means a pressure-sensitive adhesive component that accounts for 50% by mass or more of the pressure-sensitive adhesive components constituting the pressure-sensitive adhesive layer, and more than 60% by mass, more than 70% by mass, and more than 70% by mass. It means an adhesive component that accounts for 80% by mass or more, of which 90% by mass or more (including 100% by mass).

Since the acrylic pressure-sensitive adhesive has a refractive index of about 1.49, by using it as a main component of the pressure-sensitive adhesive layer laminated on the light-diffusing film, reflection at the interface between the light-diffusing film and the pressure-sensitive adhesive layer can be reduced. can be reduced.

Examples of methods for forming an adhesive layer on the light diffusion film include a method of laminating an adhesive sheet formed into a film shape with a laminator or the like, and a method of coating the light diffusion film with an adhesive.

<<Usage>>
This light diffusion film can be used for image display devices such as personal computers, televisions (TV), mobile terminals (PDA), mobile phones, smartphones, etc. Specifically, liquid crystal display devices (LCD), electroluminescence displays (ELD) ), Plasma Display Panel (PDP), Cathode Tube Display (CRT), Surface Electrolytic Display (SED), Electronic Paper, Transparent Screen, LED Diffusion Plate, Head-Up Display, TV Diffusion Plate, etc. be able to.

<<Image display device>>
In an image display device equipped with the present light diffusion film, the present light diffusion film is particularly used by bonding between the display surface of the image display device and the antireflection film, or between the antireflection film and the polarizing plate. preferably.

In addition, from the viewpoint of thinning the constituent members of the image display device, the light diffusion film may be used as a film having both the light diffusion properties and the necessary properties of the various constituent members, as a substitute for the various films of the constituent members.

When the anisotropic light-diffusing film of the present invention is used as a diffusion plate for a large liquid crystal TV having a screen of 32 inches or more, the orientation direction of the rod-shaped island phase of the film is parallel to the length direction of the cold cathode tube of the large liquid crystal TV. By arranging them so that the linear light emitted from the cold-cathode tubes can be diffused in a plane.

When the anisotropic light-diffusing film of the present invention is used in a projection type image display device, it is preferable to arrange the anisotropic light-diffusing film of the present invention as a screen in front.
Image light projected from an image display engine such as a CRT, LCD, or DMD of a projection type image display device is projected onto a screen by an optical system such as a reflecting mirror. By using a screen arranged in such a way as to scatter light to the left and right of the screen, the brightness can be improved. In particular, it is preferable when having a large screen of 32 inches or more.

<<explanation of words>>
In this specification, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" or "preferably It also includes the meaning of "smaller than Y".
In addition, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably greater than X" unless otherwise specified, and is described as "Y or less" (Y is an arbitrary number). If not otherwise specified, it also includes the meaning of "preferably smaller than Y".

The present invention is further illustrated by the following examples. However, the present invention is not limited to the examples shown below.

<Material>
The materials used in each test example are as follows.
(polycarbonate resin)
・ Resin A-1: isosorbide-based polycarbonate resin (average refractive index: 1.506, Tg: 120 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 740 Pa s, 1,4-cyclohexanedimethanol 31 .1 mol%, isosorbide 68.9 mol%)
・ Resin A-2: isosorbide-based polycarbonate resin (average refractive index: 1.516, Tg: 126 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 830 Pa s, tricyclodecanedimethanol 33.3 mol %, isosorbide 66.7 mol%)
・ Resin A-3: isosorbide-based polycarbonate resin (average refractive index: 1.502, Tg: 98 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 510 Pa s, 1,4-cyclohexanedimethanol 50 .5 mol%, isosorbide 49.5 mol%)
・ Resin A-4: isosorbide-based polycarbonate resin (average refractive index: 1.511, Tg: 126 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 680 Pa s, tricyclodecanedimethanol 33.3 mol %, isosorbide 66.7 mol%)
・ Resin A-5: polycarbonate resin (average refractive index: 1.585, Tg: 144 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 3800 Pa s))
・ Resin A-6: Polycarbonate resin (average refractive index: 1.583, Tg: 152 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 9000 Pa s, bisphenol A polycarbonate)

(amorphous polyester resin)
Resin B-1: Amorphous polyethylene terephthalate resin (average refractive index: 1.539, Tg: 109°C, apparent viscosity (240°C, 100 (1/s)): 1000 Pa s, acid component: 100 mol of terephthalic acid %, diol components: ethylene glycol 51.5 mol%, diethylene glycol 5.4 mol%, spiroglycol 43.1 mol%)
・ Resin B-2: Amorphous polyester resin (average refractive index: 1.552, Tg: 119 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 2500 Pa s, acid component: terephthalic acid 100 mol% , diol components: 1,4-cyclohexanedimethanol 65.7 mol%, 2,2,4,4-tetramethyl-1,3-cyclobutanediol 34.3 mol%)
・ Resin B-3: Amorphous polyester resin (average refractive index: 1.587, Tg: 130 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 2800 Pa s, acid component: 2,6- Naphthalene dicarboxylic acid 100 mol%, diol component: ethylene glycol 14.3 mol%, diethylene glycol 0.8 mol%, spiroglycol 37.7 mol%, 1,4-cyclohexanedimethanol 47.2 mol%)
・ Resin B-4: Amorphous polyester resin (average refractive index: 1.564, Tg: 118 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 1600 Pa s, acid component: 2,6- Naphthalene dicarboxylic acid 48.2 mol%, terephthalic acid 51.8 mol%, diol component: ethylene glycol 51.2 mol%, diethylene glycol 2.9 mol%, spiroglycol 45.9 mol%)
・ Resin B-5: polyethylene naphthalate resin (average refractive index: 1.646, Tg: 120 ° C., apparent viscosity (270 ° C., 100 (1 / s)): 2350 Pa s, acid component: 2,6-naphthalene Dicarboxylic acid 100 mol%, diol component: ethylene glycol 96.4 mol%, diethylene glycol 3.6 mol%)
・ Resin B-6: polyethylene terephthalate resin (average refractive index: 1.576, Tg: 75 ° C., apparent viscosity (270 ° C., 100 (1 / s)): 450 Pa s, acid component: terephthalic acid 100 mol%, diol Ingredient: Ethylene glycol 100mol%)

(Other resins)
- Resin C-1: acrylonitrile-styrene copolymer (AS resin) (average refractive index: 1.567, Tg: 108 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 1240 Pa s)
・ Resin C-2: cyclic polyolefin resin (average refractive index: 1.534, Tg: 138 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 3800 Pa s)
・ Resin C-3: cyclic polyolefin resin (average refractive index: 1.530, Tg: 100 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 410 Pa s)
・ Resin C-4: polystyrene resin (average refractive index: 1.589, Tg: 100 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 700 Pa s)
・ Resin C-5: polystyrene resin (average refractive index: 1.590, Tg: 100 ° C., apparent viscosity (240 ° C., 100 (1 / s)): 500 Pa s)

<Various evaluations>
Evaluation of the films and the like produced in each test example was performed as follows.

(1) Glass transition temperature The glass transition temperature (Tg) of the resin used in each test example was determined according to JIS K7121: 2012 using a differential scanning calorimeter (for example, "DSC 8500" manufactured by PerkinElmer Japan). Measurement was performed under conditions of a temperature range of 0 to 200°C and a heating rate of 10°C/min.

(2) Apparent viscosity The apparent viscosity of the resin used in each test example was measured using a Koka flow tester Shimadzu Corporation "CFT-5000" nozzle: Φ1 × 10 mm, temperature: 240 ° C. or 270 ° C. .

(3) Evaluation of the average dispersion diameter in the film thickness direction of the dispersed phase (II) In Test Example 1, the cross section of the film was photographed with a transmission electron microscope (TEM), and the maximum dispersion diameter and the minimum dispersion diameter in the photographed range were determined. It was measured and the dispersion diameter was calculated as an average value. The table shows the minimum and maximum values in parenthesis together with the average dispersion diameter.
In Test Example 2, the central part in the thickness direction of the first layer (intermediate layer) of the film (the area corresponding to ± 15% of the thickness of the light diffusion film from the center) and the front and back parts in the thickness direction (from the front or back to the main 35% of the thickness of the light diffusion film) was photographed with a transmission electron microscope (TEM), the maximum dispersion diameter and the minimum dispersion diameter in the photographed range were measured, and the average dispersion diameter was calculated. The table shows the minimum and maximum values in parenthesis together with the average dispersion diameter.
In Test Example 3, the average dispersed diameter was calculated in the same manner as in Test Example 2 except that a scanning electron microscope (SEM) was used.
In Test Example 4, the central part in the thickness direction of the first layer (intermediate layer) of the film (the area corresponding to ± 15% of the thickness of the light diffusion film from the center) and the front and back parts in the thickness direction (from the front or back to the main 35% of the thickness of the light diffusion film) is photographed with a scanning electron microscope (SEM), and the dispersion diameter in the photographing range is analyzed using the free software "ImageJ". An average dispersion diameter in the thickness direction was calculated as an average.

(4) Evaluation of the average dispersion diameter in the MD direction and the TD direction of the dispersed phase (II) In Test Example 1, each of the MD cross section and the TD cross section of the film was photographed with a transmission electron microscope (TEM), and the maximum The dispersion diameter and the minimum dispersion diameter were measured, and the average dispersion diameter was calculated. The table shows the minimum and maximum values in parenthesis together with the average dispersion diameter.
In Test Example 2, the central part in the thickness direction of the first layer (intermediate layer) of the film (the area corresponding to ± 15% of the thickness of the light diffusion film from the center) and the front and back parts in the thickness direction (from the front or back to the main 35% of the thickness of the light diffusion film) is photographed with a transmission electron microscope (TEM), the maximum dispersion diameter and the minimum dispersion diameter in the photographed range are measured, and the dispersion diameter as the average value was calculated, and the dispersion diameter ratio (MD dispersion diameter/TD dispersion diameter) was calculated from the average value. The table shows the minimum and maximum values in parenthesis together with the dispersion diameter or dispersion diameter ratio as an average value.
In Test Example 3, the average dispersed diameter was calculated in the same manner as in Test Example 2 except that a scanning electron microscope (SEM) was used.
In Test Example 4, the central part in the thickness direction of the first layer (intermediate layer) of the film (the area corresponding to ± 15% of the thickness of the light diffusion film from the center) and the front and back parts in the thickness direction (from the front or back to the main 35% of the thickness of the light diffusion film) is photographed with a scanning electron microscope (SEM), and the dispersion diameter in the photographed range is analyzed using the free software "ImageJ", and the range that can be confirmed. The average dispersion diameter in the MD direction and the TD direction was calculated as the average of all the dispersion diameters of , and the dispersion diameter ratio (MD average dispersion diameter/TD average dispersion diameter) was calculated.

(5) Average Refractive Index The average refractive index of the raw material used in each test example was measured according to JIS K7124 using an Abbe refractometer manufactured by Atago Co., Ltd., using a sodium D line (589 nm) as a light source.

(6) Refractive Index Difference The absolute value of the difference in refractive index between the continuous phase (I) and the dispersed phase (II) was defined as the refractive index difference.
When the dispersed phase (II) is composed of two types of resins, the refractive index of the dispersed phase (II) was calculated from the compounding ratio in the dispersed phase (II) and the average refractive index of each resin.

(7) Luminous reflectance R _SCI and R _SCE
In Test Example 1, a spectrophotometer ("SC-T", manufactured by Suga Test Instruments Co., Ltd.) was used, with a white calibration standard plate attached to the main unit as a reference, a black background, a D65/2 light source, and a measurement range of Φ5 mm. The luminous reflectance R _SCI and the luminous reflectance R _SCE were measured according to the method to obtain the luminous reflectance R _SCI and the luminous reflectance R _SCE .
In Test Example 2, a spectrophotometer ("CM-600d", manufactured by Konica Minolta Co., Ltd.) was used, with a white calibration standard plate attached to the main unit as a reference, a black background (R _SCI : 5.1), D65/2 Luminous reflectance R _SCI and luminous reflectance R _SCE were measured by a reflection method with a light source and a measurement range of Φ8 mm to obtain luminous reflectance R _SCI and luminous reflectance R _SCE .
In Test Example 3, a film (PET film) made of polyethylene terephthalate having a thickness of 100 μm was laminated on both sides of the film prepared in each Test Example with an adhesive layer interposed therebetween. Luminous reflectance R _SCI and luminous reflectance R _SCE were measured respectively to obtain luminous reflectance R _SCI and luminous reflectance R _SCE .
At this time, the adhesive layer was formed from a 150 μm-thick acrylic optical transparent adhesive sheet (“Clearfit (registered trademark)” manufactured by Mitsubishi Chemical Corporation).
The luminous reflectance R _SCI and the luminous reflectance R _SCE in the state where the PET film and the adhesive layer were laminated were 16.88 _{and 4.38} , respectively.
In Test Example 4, luminous reflectance R _SCI and luminous reflectance R _SCE were measured in the same manner as in Test Example 2 to obtain luminous reflectance R _SCI and luminous reflectance R _SCE .

(8) Total light transmittance The total light transmittance of the film produced in each test example was measured according to JIS K7361-1.

(9) Haze value The haze value of the film produced in each test example was measured according to JIS K7136.

(10) Luminance evaluation Using a backlight unit (Century "plus one VGA" 8 inches, model number: LCD-8000V) and a luminance meter (two-dimensional color photometer manufactured by Konica Minolta, model: CA-2000), The 60° luminance ratio and the front luminance ratio were obtained by the following methods.

(60° brightness ratio)
As shown in FIG. 1, the films 1 of Examples and Comparative Examples were fixed to a backlight unit 2, and light was made incident from the normal N direction of the film surface (thick arrow in FIG. 1). The measured value (luminance C) was confirmed when the backlight unit 2 was tilted so that the luminance meter 3 was positioned in a direction tilted 60° from the normal N direction of the film surface to the light diffusion direction y.
In addition, the measured value (luminance B) when the backlight unit 2 is arranged so that the luminance meter 3 is positioned in the direction of the normal line N was confirmed, and the ratio (C/B) of the luminance C and the luminance B was calculated. .

(front luminance ratio)
A blank sample is fixed to the backlight unit, light is incident from the normal N direction of the film surface, and the measured value (luminance A) when the backlight unit is arranged so that the luminance meter is positioned in the normal N direction After confirmation, the ratio (B/A) of the luminance B and the luminance A was calculated.
A single layer sample of Resin A was used as a blank sample. The blank sample had a total light transmittance of 92% and a haze of 0.21%.

(11) Thermal dimensional change rate In Test Example 3, the anisotropic light diffusion film of each test example was cut into a size of 12 cm × 12 cm in length and width, and tested at 110 ° C. × 60 minutes in accordance with JIS K7133: 1999. The heating dimensional change rate was measured under the conditions, and the average value of N=3 was calculated. It is shown in Table 3 as "MD direction heat shrinkage (%)".

(12) Surface hardness In Test Examples 3 and 4, the anisotropic light diffusion film of each test example was subjected to a temperature of 23 against the surface of the second layer of the sample based on JIS K5600-5-4 (1999). The test was conducted under the conditions of ±2° C., relative humidity of 50%±10° C., and load of 750 gf, and the surface hardness was measured.

(13) Surface roughness According to the method described in ISO1997, cutoff value for roughness curve: 0.8 mm, cutoff value: 2.5 μm, filter: GAUSS, Profile: R, N: contact type surface roughness as 5 height (arithmetic mean height Ra) was measured.

(14) Tensile strength Tensile strength was measured according to the method described in JIS K7161-1, with a test length of 50 mm, a test width of 15 mm, a test speed of 200 mm/min, and a test temperature of room temperature.
Also, the tensile strength ratio σ _MD /σ _TD was calculated from the tensile strength σ _MD in the MD direction and the tensile strength σ _TD in the TD direction.

<<Test Example 1>>
<Test Example 1-1>
After sufficiently mixing 60% by mass of resin A-1 and 40% by mass of resin B-1, while feeding with a constant mass feeder, extrusion kneading at 240 ° C. with a Φ 25 mm twin screw extruder (discharge rate Q ( kg/h) and the screw rotation speed N (rpm): Q/N = 0.016 (kg/h/rpm)), and cooled and solidified at a casting speed of 0.8 m/min to form an anisotropic light with a thickness of 69 µm. A diffusion film was produced.
Observation of the cross section of the obtained anisotropic light-diffusing film with a transmission electron microscope revealed that a dispersed phase composed of resin B-1 extending in the MD direction was present in the continuous phase (I) composed of resin A-1. It was confirmed that (II) has a sea-island structure in which (II) is dispersed.

<Test Example 1-2>
An anisotropic light diffusion film having a thickness of 73 μm was produced in the same manner as in Test Example 1-1, except that 60% by mass of Resin A-2 and 40% by mass of Resin B-1 were used.
When the cross section of the obtained anisotropic light diffusion film was observed with a transmission electron microscope, it was found that a dispersed phase made of resin B-1 exhibiting a shape extending in the MD direction was present in the continuous phase (I) made of resin A-2. It was confirmed that (II) has a sea-island structure in which (II) is dispersed.

<Test Example 1-3>
An anisotropic light diffusion film having a thickness of 72 μm was produced in the same manner as in Test Example 1-1, except that 60% by mass of Resin A-1 and 40% by mass of Resin B-2 were used.
Observation of the cross section of the obtained anisotropic light-diffusing film with a transmission electron microscope revealed that a dispersed phase made of resin B-2, which had a shape extending in the MD direction, was present in the continuous phase (I) made of resin A-1. It was confirmed that (II) has a sea-island structure in which (II) is dispersed.

<Test Example 1-4>
An anisotropic light diffusion film having a thickness of 69 μm was produced in the same manner as in Test Example 1-1 except that 60% by mass of Resin A-2 and 40% by mass of Resin B-2 were used.
Observation of the cross section of the obtained anisotropic light-diffusing film with a transmission electron microscope revealed that a dispersed phase composed of resin B-2 exhibiting a shape extending in the MD direction was present in the continuous phase (I) composed of resin A-2. It was confirmed that (II) has a sea-island structure in which (II) is dispersed.

<Test Example 1-5>
After thoroughly mixing 60% by mass of resin A-5 and 40% by mass of resin B-5, while feeding with a constant mass feeder, extrusion kneading at 280 ° C. with a Φ 25 mm twin screw extruder (discharge amount Q (kg /h) and the screw rotation speed N (rpm) ratio: Q/N = 0.043 (kg/h/rpm)), and cooled and solidified at a casting speed of 1.9 m/min to form an anisotropic light diffusion film with a thickness of 60 μm. A film was produced.
When the cross section of the obtained film was observed with a transmission electron microscope, it was found that the dispersed phase (II) made of resin B-5, which had a shape extending in the MD direction, was present in the continuous phase (I) made of resin A-5. was confirmed to have a sea-island structure in which

<Test Example 1-6>
After thoroughly mixing 60% by mass of resin B-3, 28% by mass of resin B-5 and 12% by mass of resin B-6, extruding at 280 ° C. with a Φ 25 mm twin screw extruder while feeding with a constant mass feeder. Knead (ratio of discharge rate Q (kg/h) and screw rotation speed N (rpm): Q/N = 0.043 (kg/h/rpm)), and cool and solidify at a casting speed of 1.5 m/min. A film with a thickness of 160 μm was produced by
The resulting film was cut out, tilted at 90°, passed through a tenter heated to a stretching temperature of 150°C, and stretched 3 times in the MD to produce an anisotropic light diffusion film with a thickness of 68 µm.
When the cross section of the obtained film was observed with a transmission electron microscope, it was found that the continuous phase (I) made of resin B-3 had a shape extending in the MD direction, made of resin B-5 and resin B-6. It was confirmed to have a sea-island structure in which the dispersed phase (II) is dispersed.

<Test Example 1-7>
After sufficiently mixing 60% by mass of resin B-1 and 40% by mass of resin B-6, while feeding with a constant mass feeder, extrusion kneading at 280 ° C. with a Φ 25 mm twin screw extruder (discharge Q (kg / h) and the screw rotation speed N (rpm): Q/N = 0.046 (kg/h/rpm)), and cooled and solidified at a casting speed of 4.7 m/min to produce a film with a thickness of 62 µm. .
When the cross section of the obtained film was observed with a transmission electron microscope, it was found that the dispersed phase (II) made of resin B-6, which had a shape extending in the MD direction, was present in the continuous phase (I) made of resin B-1. was confirmed to have a sea-island structure in which

Each of the anisotropic light diffusion films obtained in Test Examples 1-1 to 1-4 has a sea-island structure in which the dispersed phase (II) having a shape extending in the MD direction is dispersed in the continuous phase (I). The continuous phase (I) contained a thermoplastic resin having an average refractive index of 1.53 or less.
From the above test examples and the results of the tests conducted by the present inventors so far, it has been found that the If at least one of them contains a thermoplastic resin having an average refractive index of 1.53 or less, it can be considered that both anisotropic light diffusibility and low reflectivity can be achieved.

In addition, the anisotropic light diffusion films obtained in Test Examples 1-3 and 1-4 had dispersion diameters in the TD direction and thickness direction as compared with the films obtained in Test Examples 1-5 to 1-7. It was large, and the ratio of dispersion diameter (MD dispersion diameter/TD dispersion diameter) and refractive index difference were more appropriate. Test Examples 1-1 and 1-2 also contain a thermoplastic resin having an average refractive index of 1.53 or less, and the refractive index difference between the continuous phase (I) and the dispersed phase (II) is about the same. Therefore, it is estimated that the dispersion diameters in the thickness direction, the MD direction and the TD direction and the ratio of the dispersion diameters (MD dispersion diameter/TD dispersion diameter) are approximately the same as those in Test Examples 1-3 and 1-4. Therefore, the anisotropic light diffusing films obtained in Test Examples 1-1 to 1-4 have further excellent anisotropic light diffusibility for diffusing light in a specific direction and low reflectivity. can be considered to exist.

<<Test Example 2>>
<Test Example 2-1>
As the composition for forming the first layer, 60% by mass of resin A-1 and 40% by mass of resin B-2 are sufficiently mixed, and preheated using an oven to hold at 110 ° C. for 6 hours. , extruder (cylinder temperature: 240 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 5.6 × 10 ^-3 (kg / h / rpm)) and melted.
In addition, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110 ° C. for 6 hours, and then extruded (cylinder temperature: 240 ° C., discharge amount Q (kg / h) and the ratio of screw rotation speed N (rpm): Q/N=6.8×10 ⁻³ (kg/h/rpm)) and melted.
After that, it is cooled and solidified at a casting speed of 3.6 m / min, and an anisotropic light diffusion film with a thickness of 90 μm with a first layer having a thickness of 68 μm as an intermediate layer and a second layer having a total thickness of 22 μm as front and back layers ( second layer/first layer/second layer: 11 μm/68 μm/11 μm).

A cross section of the obtained anisotropic light-diffusing film was observed with a transmission electron microscope. A first layer having a sea-island structure in which the dispersed phase (I) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .

<Test Example 2-2>
When forming the first layer, the extruder (cylinder temperature: 240 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 2.4 × 10 ^-1 (kg / h / rpm)), and when forming the second layer, the extruder (cylinder temperature: 240 ° C., the ratio of the discharge rate Q (kg / h) and the screw rotation speed N (rpm): Q /N = 6.8 × ^{10 -3} (kg / h / rpm)) and cooled and solidified at a casting speed of 2.0 m / min. A diffusion film (second layer/first layer/second layer: 20 μm/35 μm/20 μm) was prepared.

A cross section of the obtained anisotropic light-diffusing film was observed with a transmission electron microscope. A first layer having a sea-island structure in which the dispersed phase (I) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 2-3>
As the composition for forming the first layer, 60% by mass of Resin A-3 and 40% by mass of Resin B-2 were thoroughly mixed and preheated using an oven to hold at 90° C. for 6 hours. Further, as the second layer-forming composition, the same procedure as in Test Example 2-2 was performed except that resin A-3 was preheated in an oven so as to be held at 90° C. for 6 hours, and then supplied to the extruder. Thus, an anisotropic light diffusion film (second layer/first layer/second layer: 19.5 μm/34 μm/19.5 μm) having a thickness of 73 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a transmission electron microscope, it was found that the continuous phase (II) made of the resin A-3 was composed of the resin B-2 exhibiting a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (I) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 2-4>
An anisotropic light diffusion film having a thickness of 69 μm (first 2 layers/first layer/second layer: 18.5 μm/32 μm/18.5 μm).

A cross section of the obtained anisotropic light-diffusing film was observed with a transmission electron microscope. A first layer having a sea-island structure in which the dispersed phase (I) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 2-5>
As the composition for forming the first layer, 60% by mass of Resin A-3 and 40% by mass of Resin B-2 were thoroughly mixed and preheated using an oven to hold at 90° C. for 6 hours. Further, when forming the second layer, resin A-1 was extruded (cylinder temperature: 230 ° C., ratio of discharge amount Q (kg / h) and screw rotation speed N (rpm): Q / N = 7.0 × 10 ^-3 (kg/h/rpm)) and cooled and solidified at a casting speed of 2.2 m/min in the same manner as in Test Example 2-2, an anisotropic light diffusion film (second layer /first layer/second layer: 18.5 μm/31 μm/18.5 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a transmission electron microscope, it was found that the continuous phase (II) made of the resin A-3 was composed of the resin B-2 exhibiting a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (I) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 2-6>
60% by mass of resin A-5 and 40% by mass of resin B-5 were thoroughly mixed, preheated in an oven to hold at 120° C. for 6 hours, and then supplied by a constant mass feeder. Supplied to the extruder (cylinder temperature: 280 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 4.3 × 10 ^-2 (kg / h / rpm)) melted. After that, it was cooled and solidified at a casting speed of 1.9 m/min to prepare a film having a thickness of 72 μm.

When the cross section of the obtained film was observed with a transmission electron microscope, it was found that the dispersed phase ( It was confirmed that I) has a dispersed sea-island structure.

In all of the anisotropic light-diffusing films obtained in Test Examples 2-1 to 2-4, the size of the dispersed phase (I) was not significantly different between the central portion in the thickness direction and the front and back portions in the thickness direction. Test Example 2-5 also has a second layer, and the refractive index difference between the continuous phase (I) and the dispersed phase (II) is about the same. , the dispersion diameters in the thickness direction, the MD direction and the TD direction and the ratio of the dispersion diameters (MD dispersion diameter/TD dispersion diameter) are estimated to be approximately the same as in Test Examples 2-1 to 2-4.
From the above test examples and the results of tests conducted by the present inventors so far, by forming the continuous phase of the two layers from the same type of thermoplastic resin, it is possible to achieve both anisotropic light diffusion and low reflectivity. can be thought of as
All of the anisotropic light diffusion films obtained in Test Examples 2-1 to 2-5 had both high brightness and anisotropic light diffusion. It also had low reflectivity.

<<Test Example 3>>
<Test Example 3-1>
As the composition for forming the first layer, 60% by mass of resin A-4 and 40% by mass of resin B-2 are thoroughly mixed, and preheated using an oven so as to be held at 110 ° C. for 17 hours. , extruder (cylinder temperature: 230 to 240 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 2.4 × 10 ^-1 (kg / h / rpm)) and melted.
On the other hand, as the composition for forming the second layer, resin A-4 was preheated using an oven so as to be held at 110° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 230 to 240° C.). melted.
After that, it is cooled and solidified at a casting speed of 2.0 m / min, and an anisotropic light diffusion film with a thickness of 62 μm (with a first layer having a thickness of 29 μm as an intermediate layer and a second layer having a total thickness of 33 μm as front and back layers) second layer/first layer/second layer: 16.5 μm/29 μm/16.5 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) composed of resin A-4 was composed of resin B-2, which exhibited a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .

<Test Example 3-2>
As the composition for forming the first layer, 60% by mass of Resin A-1 and 40% by mass of Resin B-2 were thoroughly mixed and preheated using an oven to hold at 110° C. for 17 hours.
On the other hand, as the second layer-forming composition, Resin A-1 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder, except that it was supplied to the extruder. Similarly, an 81 μm-thick anisotropic light diffusion film (second layer/first layer/second layer: 25.5 μm/30 μm/25.5 μm) was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of the resin A-1 was made of the resin B-2 exhibiting a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-3>
As the composition for forming the first layer, 60% by mass of Resin A-1 and 40% by mass of Resin B-2 were thoroughly mixed and preheated using an oven to hold at 110° C. for 17 hours.
On the other hand, as the second layer-forming composition, resin A-4 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder Same as Test Example 3-1. Then, an anisotropic light diffusion film (second layer/first layer/second layer: 23.5 μm/29 μm/23.5 μm) having a thickness of 76 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of the resin A-1 was made of the resin B-2 exhibiting a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-4>
As the first layer-forming composition, 59% by weight of Resin A-4 and 41% by weight of Resin C-1 were thoroughly mixed and preheated using an oven to hold at 85° C. for 17 hours.
On the other hand, as the second layer-forming composition, resin A-4 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder Same as Test Example 3-1. Then, an anisotropic light diffusion film (second layer/first layer/second layer: 19 μm/29 μm/19 μm) having a thickness of 67 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) composed of resin A-4 was composed of resin C-1, which exhibited a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-5>
As the composition for forming the first layer, 55% by weight of Resin A-4 and 45% by weight of Resin B-4 were thoroughly mixed and preheated using an oven to hold at 110° C. for 17 hours.
On the other hand, as the second layer-forming composition, resin A-4 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder Same as Test Example 3-1. Then, an anisotropic light diffusion film (second layer/first layer/second layer: 18 μm/29 μm/18 μm) having a thickness of 65 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of resin A-4 was made of resin B-4, which exhibited a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-6>
As the composition for forming the first layer, 59% by weight of Resin A-1 and 41% by weight of Resin C-1 were thoroughly mixed and preheated using an oven to hold at 85° C. for 17 hours.
On the other hand, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder Same as Test Example 3-1. Then, an anisotropic light diffusion film (second layer/first layer/second layer: 25.5 μm/29 μm/25.5 μm) having a thickness of 80 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of resin A-1 was made of resin C-1, which exhibited a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-7>
As the composition for forming the first layer, 55% by mass of Resin A-1 and 45% by mass of Resin B-4 were thoroughly mixed and preheated using an oven to hold at 110° C. for 17 hours.
On the other hand, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to the extruder Same as Test Example 3-1. Then, an anisotropic light diffusion film (second layer/first layer/second layer: 22.5 μm/28 μm/22.5 μm) having a thickness of 73 μm was produced.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of resin A-1 was made of resin B-4, which exhibited a shape extending in the MD direction. A first layer having a sea-island structure in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.

<Test Example 3-8>
60% by mass of resin A-5 and 40% by mass of resin B-5 were thoroughly mixed, preheated in an oven to hold at 120° C. for 6 hours, and then supplied by a constant mass feeder. Supplied to the extruder (cylinder temperature: 280 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 4.3 × 10 ^-2 (kg / h / rpm)) melted. After that, it was cooled and solidified at a casting speed of 1.9 m/min to prepare a film having a thickness of 72 μm.

When the cross section of the obtained film was observed with a scanning electron microscope, it was found that the dispersed phase ( It was confirmed that II) has a dispersed sea-island structure.

All of the anisotropic light diffusion films obtained in Test Examples 3-1 to 3-7 had surface hardness and heat resistance. In addition, in the anisotropic light diffusion films obtained in Test Examples 3-1 to 3-7, the size of the dispersed phase (I) did not change greatly between the central portion in the thickness direction and the front and back portions in the thickness direction. It was also excellent in low reflectivity.
On the other hand, Test Example 3-8 was inferior in low reflectivity and had low surface hardness although the glass transition temperature of the second layer was high.

<<Test Example 4>>
<Test Example 4-1>
As the first layer-forming composition, 58% by mass of resin A-3 and 42% by mass of resin B-4 are thoroughly mixed, preheated using an oven to hold at 90 ° C. for 17 hours, and then extruded. (Cylinder temperature: 220 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 2.4 × 10 ^-1 (kg / h / rpm)) and melted bottom.
In addition, as the second layer-forming composition, resin A-3 was preheated using an oven so as to be held at 90° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 220° C.) and melted. bottom.
After that, it is cooled and solidified at a casting speed of 2.2 m/min to form an anisotropic light diffusion film having a thickness of 83 μm (second layer/first layer/second layer: 24.5 μm/34 μm/24.5 μm). made.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of the resin A-3 was made of the resin B-4 exhibiting a shape extending in the MD direction. A first layer in which the dispersed phase (II) is dispersed was confirmed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .
FIGS. 2 and 3 show the MD cross section and TD cross section of the anisotropic light diffusion film of Test Example 4-1, respectively. Arrows in the figure indicate the interface between the first layer and the second layer.

<Test Example 4-2>
In the same manner as in Test Example 4-2 except that 58% by mass of resin A-3, 5% by mass of resin B-3, and 37% by mass of resin B-4 were used as the first layer-forming composition, the thickness was 82 μm. of the anisotropic light diffusion film (second layer/first layer/second layer: 24.5 μm/33 μm/24.5 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, resin B-3 and resin A first layer in which the dispersed phase (II) composed of B-4 was dispersed was confirmed. It is believed that Resin B-3 and Resin B-4 are compatible in dispersed phase (II) since no further dispersed components were observed in dispersed phase (II).
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .
FIGS. 4 and 5 show the MD cross section and TD cross section of the anisotropic light diffusion film of Test Example 4-2, respectively. Arrows in the figure indicate the interface between the first layer and the second layer.

<Test Example 4-3>
As the composition for forming the first layer, 60% by mass of resin A-4, 20% by mass of resin A-6 and 20% by mass of resin B-2 are sufficiently mixed and kept at 110 ° C. for 17 hours using an oven. After preheating to , extruder (cylinder temperature: C2 to C9: 265 ° C., ratio of discharge amount Q (kg / h) and screw rotation speed N (rpm): Q / N = 2.4 × 10 ^-1 ( kg/h/rpm)) and melted.
In addition, as the second layer-forming composition, resin A-4 was preheated using an oven so as to be held at 110 ° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 250 ° C.) and melted. bottom.
After that, it was cooled and solidified at a casting speed of 2.2 m/min to produce an anisotropic light diffusion film having a thickness of 72 μm (second layer/first layer/second layer: 21 μm/30 μm/21 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, resin A-6 and resin A first layer in which the dispersed phase (II) composed of B-2 was dispersed was confirmed. It is believed that resin A-6 and resin B-2 are phase-separated in dispersed phase (II), since a component further dispersed in dispersed phase (II) was observed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .
FIGS. 6 and 7 show MD cross sections and TD cross sections of the anisotropic light diffusion film of Test Example 4-3, respectively. Arrows in the figure indicate the interface between the first layer and the second layer.

<Test Example 4-4>
As the composition for forming the first layer, 55% by mass of resin A-1, 20% by mass of resin A-6 and 25% by mass of resin B-2 are thoroughly mixed and extruded (cylinder temperature: C2 to C5: 260 ° C. , C5-C9: 230°C, ratio of discharge rate Q (kg/h) and screw rotation speed N (rpm): Q/N = 2.4 × 10 ^-1 (kg/h/rpm)) melted.
In addition, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 230° C.) and melted. bottom.
After that, it was cooled and solidified at a casting speed of 2.2 m/min to form an anisotropic light diffusion film having a thickness of 78 μm (second layer/first layer/second layer: 23.5 μm/31 μm/23.5 μm). made.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, resin A-6 and resin A first layer in which the dispersed phase (II) composed of B-2 was dispersed was confirmed. It is believed that resin A-6 and resin B-2 are phase-separated in dispersed phase (II), since a component further dispersed in dispersed phase (II) was observed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .
FIGS. 8 and 9 show the MD cross section and TD cross section of the anisotropic light diffusion film of Test Example 4-4, respectively. Arrows in the figure indicate the interface between the first layer and the second layer.

<Test Example 4-5>
As the composition for forming the first layer, 59% by mass of resin A-1, 16% by mass of resin B-1 and 25% by mass of resin B-3 are sufficiently mixed and extruded (cylinder temperature: 230 ° C., discharge amount Q (kg/h) and screw rotation speed N (rpm) ratio: Q/N=2.4×10 ⁻¹ (kg/h/rpm)) and melted.
In addition, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 230° C.) and melted. bottom.
After that, it was cooled and solidified at a casting speed of 2.2 m/min to form an anisotropic light diffusion film having a thickness of 78 μm (second layer/first layer/second layer: 25.5 μm/27 μm/25.5 μm). made.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that resin B-1 and resin A first layer in which the dispersed phase (II) composed of B-3 was dispersed was confirmed. It is believed that resin B-1 and resin B-3 are phase-separated in dispersed phase (II), since a component further dispersed in dispersed phase (II) was observed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .

<Test Example 4-6>
As the composition for forming the first layer, 61% by mass of resin A-1, 23% by mass of resin B-3 and 16% by mass of resin C-2 are sufficiently mixed, extruder (cylinder temperature 240 ° C., discharge amount Q ( (kg/h) and the screw rotation speed N (rpm): Q/N=2.4×10 ⁻¹ (kg/h/rpm)) and melted.
In addition, as the second layer-forming composition, resin A-1 was preheated using an oven so as to be held at 110° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 230° C.) and melted. bottom.
After that, it was cooled and solidified at a casting speed of 2.2 m/min to produce an anisotropic light diffusion film having a thickness of 76 μm (second layer/first layer/second layer: 25 μm/26 μm/25 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, resin B-3 and resin A first layer in which dispersed phase (II) consisting of C-2 was dispersed was confirmed. It is believed that resin B-3 and resin C-2 are phase-separated in dispersed phase (II), since a component further dispersed in dispersed phase (II) was observed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .

<Test Example 4-7>
As the first layer-forming composition, 56% by mass of resin C-3 and 44% by mass of resin C-4 were thoroughly mixed, preheated using an oven to hold at 70 ° C. for 17 hours, and then extruded. (Cylinder temperature: 230 ° C., ratio of discharge rate Q (kg / h) and screw rotation speed N (rpm): Q / N = 2.4 × 10 ^-1 (kg / h / rpm)) and melted bottom.
In addition, as the second layer-forming composition, resin C-3 is preheated using an oven so as to be held at 70 ° C. for 17 hours, and then supplied to an extruder (cylinder temperature: 230 ° C.) and melted. bottom.
After that, it was cooled and solidified at a casting speed of 2.2 m/min to form an anisotropic light diffusion film having a thickness of 77 μm (second layer/first layer/second layer: 22.5 μm/32 μm/22.5 μm). made.

A cross section of the obtained anisotropic light-diffusing film was observed with a scanning electron microscope. A first layer was identified in which phase (II) was dispersed.
It was also confirmed that the second layer did not have a dispersed phase.
At this time, the first layer contains a dispersed phase, and the dispersed phase can be confirmed up to the interface with the second layer, so the interface between the first layer and the second layer was confirmed. .
FIGS. 10 and 11 show the MD cross section and TD cross section of the anisotropic light diffusion film of Test Example 4-7, respectively. Arrows in the figure indicate the interface between the first layer and the second layer.

<Test Example 4-8>
An anisotropic light diffusion film having a thickness of 75 μm (first 2 layers/first layer/second layer: 21.5 μm/32 μm/21.5 μm).

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of resin C-3 was made of resin C-4, which exhibited a shape extending in the MD direction. It was confirmed to have a sea-island structure in which the dispersed phase (II) is dispersed.
Since the dispersed phase in the first layer was small, the interface between the first layer and the second layer could not be confirmed.
FIGS. 12 and 13 show the MD cross section and TD cross section of the anisotropic light diffusion film of Test Example 4-8, respectively.

<Test Example 4-9>
As the composition for forming the first layer, 60% by mass of resin A-5 and 40% by mass of resin C-4 are sufficiently mixed, and an extruder (cylinder temperature: 250 ° C., discharge rate Q (kg / h) and screw rotation A ratio of several N (rpm): Q/N=2.4×10 ⁻¹ (kg/h/rpm)) and melted.
Then, it was cooled and solidified at a casting speed of 3.0 m/min to produce an anisotropic light diffusion film (first layer: 60 μm) with a thickness of 60 μm.

When the cross section of the obtained anisotropic light diffusion film was observed with a scanning electron microscope, it was found that the continuous phase (I) made of resin A-5 was made of resin C-4, which exhibited a shape extending in the MD direction. A first layer in which the dispersed phase (II) is dispersed was confirmed. Since the dispersed phases in the front and back portions in the thickness direction were too small to be observed, the diameters of the dispersed phases in the front and back portions were not measured.

All of the anisotropic light diffusion films obtained in Test Examples 4-1 to 4-6 have a 60° luminance ratio/front luminance ratio within the preferred range of the present invention, a high 60° luminance ratio, and all light rays It also has excellent transmittance and low reflectivity. Therefore, by adjusting the 60° luminance ratio/front luminance ratio, it can be said that the front luminance and the anisotropic light diffusion property are well balanced, and the brightness and visibility at a wide viewing angle are improved when mounted on a display.

In addition, all of the anisotropic light diffusion films obtained in Test Examples 4-1 to 4-6 are formed by dispersing the dispersed phase (II) exhibiting a shape extending in the MD direction in the continuous phase (I). It has a sea-island structure and high haze, so it contains a large amount of dispersion components and is excellent in anisotropic light diffusion. In addition, the tensile strength is within the preferred range of the present invention, and the anisotropy of the tensile strength is small, so it is thought that interfacial separation between the continuous phase (I) and the dispersed phase (II) is unlikely to occur. It can be said that the reflection is small, ie, the low reflectivity is excellent, and the total light transmittance is high.

Furthermore, in all of the anisotropic light diffusion films obtained in Test Examples 4-1 to 4-6, the average dispersion diameter in the MD direction with respect to the average dispersion diameter in the TD direction at the center in the thickness direction of the first layer The ratio (MD average dispersion diameter/TD average dispersion diameter) is within the preferred range of the present invention, and the anisotropic light diffusibility is excellent. In addition, since the dispersed phase volume in the central part in the thickness direction and the dispersed phase area in the TD cross section are within the preferable range of the present invention, the dispersed diameter in the TD direction and the thickness direction are moderately large, so per dispersed phase In addition, since the dispersion diameter in the TD direction and the thickness direction does not become too large, it has strong diffusivity in the vicinity of the direction inclined 60° from the normal N direction of the light diffusion film surface to the light diffusion direction. It can be said that an ideal island component can be formed and an optimum dispersion structure can be obtained to further enhance the anisotropic light diffusibility.

In the anisotropic light diffusion films obtained in Test Examples 4-7 to 4-9, the 60° luminance ratio/front luminance ratio is smaller than the preferred range of the present invention, and the low reflectivity is Test Examples 4-1 to 4- 6, but inferior in 60° luminance ratio and total light transmittance. In other words, it can be said that the anisotropic light diffusion films of Test Examples 4-7 to 4-9 have low anisotropic light diffusion properties and low transmittance, and are insufficient in brightness and visibility when mounted on a display.

The anisotropic light diffusion film obtained in Test Example 4-7 had a sea-island structure in which the dispersed phase (II) having a shape extending in the MD direction was dispersed in the continuous phase (I). Since the haze is high, it contains many dispersed components, but the tensile strength is low and the anisotropy of the tensile strength is large. It is considered that the control of the diameter is difficult and the anisotropic light diffusing property tends to be low. In addition, since the volume of the dispersed phase at the central portion in the thickness direction is larger than the preferred range of the present invention, the dispersion diameters in the TD direction and the thickness direction become too large, and the light diffuses from the normal N direction of the surface of the light diffusion film. An ideal island component having a strong diffusivity cannot be formed in the vicinity of a direction inclined 60° to the direction, and it can be considered that the anisotropic light diffusibility is inferior to that of Test Examples 4-1 to 4-6. can.
The anisotropic light diffusion film obtained in Test Example 4-8 has low anisotropy in tensile strength, so interfacial separation between the continuous phase (I) and the dispersed phase (II) is unlikely to occur, and the interfacial reflection is small. Although it has excellent low reflectivity, the haze is low, so the dispersion component is small. /TD average dispersion diameter) is smaller than the preferred range of the present invention, and it can be said that the anisotropic light diffusing property is inferior. In addition, since the volume of the dispersed phase at the central portion in the thickness direction is smaller than the preferred range of the present invention, the dispersion diameter in the TD direction and the thickness direction is small, so that the reflection per dispersed phase is large, and the present light diffusion An ideal island component with strong diffusivity could not be formed in the vicinity of the direction inclined 60° from the normal N direction of the film surface to the light diffusion direction, which was different from Test Examples 4-1 to 4-6. It can be considered that the directional light diffusion is inferior.
The anisotropic light diffusion film obtained in Test Example 4-9 has a large anisotropy of tensile strength, so interfacial separation between the continuous phase (I) and the dispersed phase (II) is likely to occur, and the interfacial reflection is large and low. It can be said that the reflectivity is inferior. Moreover, since the refractive index difference between the continuous phase (I) and the dispersed phase (II) is very small, it can be said that the anisotropic light diffusibility is inferior. In addition, since the volume of the dispersed phase at the central portion in the thickness direction is smaller than the preferred range of the present invention, the dispersion diameter in the TD direction and the thickness direction is small, so that the reflection per dispersed phase is large, and the present light diffusion An ideal island component with strong diffusivity could not be formed in the vicinity of the direction inclined 60° from the normal N direction of the film surface to the light diffusion direction, which was different from Test Examples 4-1 to 4-6. It can be considered that the directional light diffusion is inferior.

Since this light diffusion film has excellent brightness and visibility when mounted on a display, it is particularly useful for image display devices such as personal computers, televisions, mobile terminals (PDA), mobile phones, smartphones, transparent screens, and LED diffusion plates. And it can be used as a component (diffusion member) such as a head-up display.

Claims (28)

1. A light diffusion film having at least a first layer capable of scattering incident light in the direction of travel of the light,
   An anisotropic light-diffusing film having a ratio of 60° brightness ratio to front brightness ratio (60° brightness ratio/front brightness ratio) determined by the following method of 0.30 or more and 0.60 or less.
   <60° brightness ratio>
   In the light diffusion film, the ratio (C/B) of the luminance C in the direction inclined 60° from the normal N direction of the film surface to the light diffusion direction and the front luminance B in the normal N direction of the film surface is 60° Let it be the luminance ratio.
   <Front luminance ratio>
   The ratio (B/A) of the front luminance B of the light diffusion film and the front luminance A in the normal N direction of the film surface in the blank sample satisfying the following conditions (1) and (2) is defined as the front luminance ratio. do.
   [Blank sample]
   (1) The total light transmittance measured according to JIS K7361-1 is 90% or more.
   (2) The haze measured according to JIS K7136 is 1% or less.
2. The anisotropic light diffusion film according to claim 1, wherein the 60° luminance ratio is 27% or more.
3. The anisotropic light diffusion film according to claim 1, wherein the front luminance ratio is 80% or more.
4. The anisotropic light diffusion film according to claim 1, which has a surface hardness of B or higher.
5. The anisotropic light-diffusing film according to claim 1, wherein the arithmetic mean height Ra is 10 µm or less.
6. The anisotropic light-diffusing film according to claim 1, which has a haze of 40% or more as measured according to JIS K7136.
7. The anisotropic light diffusion film according to claim 1, which has a total light transmittance of 94% or more.
8. The ratio (R SCE /R SCI ) between the luminous reflectance R _SCE of the specular component exclude method and the luminous reflectance R _SCI of the specular component include method (R _SCE /R _SCI ) is 50 % or more, the anisotropic light-diffusing film of claim 1.
9. The anisotropic light-diffusing film according to claim 1, wherein the first layer has a sea-island structure with a continuous phase (I) and a dispersed phase (II).
10. 10. The anisotropic light-diffusing film according to claim 9, wherein the dispersed phase volume at the central portion in the thickness direction of the first layer is 20 μm ³ or more and 120 μm ³ or less.
11. 10. The ratio of the average dispersion diameter in the MD direction to the average dispersion diameter in the TD direction of the dispersed phase (II) (MD average dispersion diameter/TD average dispersion diameter) is 3 or more at the center in the thickness direction. An anisotropic light-diffusing film as described.
12. 10. The anisotropic light-diffusing film according to claim 9, wherein the dispersed phase (II) has a dispersion diameter area of 2 μm ³ or more in the TD cross section at the central portion in the thickness direction.
13. 10. The anisotropic light-diffusing film according to claim 9, wherein both the tensile strength _σMD in the MD direction and the tensile strength _σTD in the TD direction are 50 MPa or more.
14. 2. The anisotropic light-diffusing film according to claim 1, wherein the first layer contains a polycarbonate resin containing a structural unit (a) derived from a dihydroxy compound represented by the following general formula (1).
    

    
15. The anisotropic light-diffusing film according to claim 14, wherein the polycarbonate resin further contains a structural unit (b) derived from a dihydroxy compound other than the structural unit (a).
16. The anisotropic light-diffusing film according to claim 15, wherein the structural unit (b) is a structural unit derived from an aliphatic dihydroxy compound and/or a structural unit derived from an alicyclic dihydroxy compound.
17. 17. The anisotropic light diffusion film according to claim 16, wherein the alicyclic dihydroxy compound is one or more selected from cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol and pentacyclopentadecanedimethanol. .
18. The anisotropic light diffusion film according to claim 1, wherein the first layer contains an amorphous polyester resin.
19. The anisotropic light diffusion film according to claim 18, wherein the amorphous polyester resin contains a diol component having an alicyclic structure.
20. The claim that the diol component having an alicyclic structure is one or more selected from spiroglycol, isosorbide, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. 20. The anisotropic light diffusion film according to 19.
21. The anisotropic light diffusion film according to claim 1, wherein the first layer contains two or more types of amorphous polyester resins.
22. The first layer contains an amorphous polyester resin and a polycarbonate resin (excluding a polycarbonate resin containing a structural unit (a) derived from a dihydroxy compound represented by the following general formula (1)). The anisotropic light-diffusing film of claim 1.
    

    
23. The anisotropic light diffusion film according to claim 1, having a second layer on at least one surface of the first layer.
24. The anisotropic light-diffusing film according to claim 23, wherein the second layer has substantially no dispersed phase.
25. An anisotropic light-diffusing film with an adhesive layer, which has an adhesive layer on at least one surface of the anisotropic light-diffusing film according to claim 1.
26. The anisotropic light-diffusing film with an adhesive layer according to claim 25, wherein the adhesive layer contains an acrylic adhesive.
27. An image display device comprising the anisotropic light diffusion film according to claim 1.
28. 28. The image display device according to claim 27, wherein the screen size is 32 inches or more.
    

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